Let <
span id="mml
si1" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si1.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=1e6227abaf358996ae54ab98f58ffbbb" title="Click to view the MathML
source">k
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span> be a po
sitive integer. A
sequence <
span id="mml
si3" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si3.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=de3a2a1fa97af36a0e06e15e46e99398" title="Click to view the MathML
source">
s<
sub>1
sub>,
s<
sub>2
sub>,…,
s<
sub>m
sub>
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span> over an <
span id="mml
si4" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si4.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=154071badf340ab9089c0eee55da54d5" title="Click to view the MathML
source">n
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span>-element <
span id="mml
si5" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si5.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=50343e1219052bd4c5cdf12d185067ce" title="Click to view the MathML
source">A
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span> alphabet i
s a
packing <
span id="mml
si1" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si1.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=1e6227abaf358996ae54ab98f58ffbbb" title="Click to view the MathML
source">k
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span>
-radius sequence , if for all pair
s of indice
s <
span id="mml
si7" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si7.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=ade580d12482c737dba0f59254eb7c5b" title="Click to view the MathML
source">(i,j)
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span>,
such that <
span id="mml
si8" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si8.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=a8799435e45f35cf9b3ccab4f4c975c1" title="Click to view the MathML
source">1≤i<j≤m
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span> and <
span id="mml
si9" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si9.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=27292dafc7cac7921a8b504eaa5c1f04" title="Click to view the MathML
source">j&minu
s;i≤k
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span>, the
set
s <
span id="mml
si10" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si10.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=14dd50401ed229dc00859064d01d5c84" title="Click to view the MathML
source">{
s<
sub>i
sub>,
s<
sub>j
sub>}
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span> are pairwi
se different <
span id="mml
si11" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si11.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=1959b84aa585f2bca3d
de120f856d5b0" title="Click to view the MathML
source">2
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span>-element
sub
set
s of <
span id="mml
si5" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si5.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=50343e1219052bd4c5cdf12d185067ce" title="Click to view the MathML
source">A
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span>. Let <
span id="mml
si13" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si13.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=1cc020038412efed175a6c7f7cbfd736" title="Click to view the MathML
source">g<
sub>k
sub>(n)
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span> denote the length of a longe
st <
span id="mml
si1" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si1.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=1e6227abaf358996ae54ab98f58ffbbb" title="Click to view the MathML
source">k
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span>-radiu
s sequence over <
span id="mml
si5" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si5.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=50343e1219052bd4c5cdf12d185067ce" title="Click to view the MathML
source">A
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span>. We give a con
struction demon
strating that for every <
span id="mml
si16" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si16.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=c7548b87a6a545e246719d1562d91366" title="Click to view the MathML
source">k=⌊cn<
sup>α
sup>⌋
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span>, where <
span id="mml
si17" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si17.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=5d3e528acdda79ed5281ba6363311246" title="Click to view the MathML
source">c
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span> and <
span id="mml
si18" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si18.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=4eb7e9caf679c33bc51b2a9d15c0ff99" title="Click to view the MathML
source">α
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span> are fixed real
s such that <
span id="mml
si19" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si19.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=9e87bcf4fd9232111b181392172644c9" title="Click to view the MathML
source">c>0
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span> and <
span id="mml
si20" cla
ss="mathml
src">
source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0195669816300063&_mathId=si20.gif&_user=111111111&_pii=S0195669816300063&_rdoc=1&_issn=01956698&md5=df2e1021f9daf578abbae5351d7a166e">ss="imgLazyJSB inlineImage" height="21" width="72" alt="View the MathML source" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0195669816300063-si20.gif">script>style="vertical-align:bottom" width="72" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S0195669816300063-si20.gif">script><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span>, <
span id="mml
si21" cla
ss="mathml
src">
source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0195669816300063&_mathId=si21.gif&_user=111111111&_pii=S0195669816300063&_rdoc=1&_issn=01956698&md5=2f09c655c963bcc71db5a6b216626628">ss="imgLazyJSB inlineImage" height="24" width="142" alt="View the MathML source" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0195669816300063-si21.gif">script>style="vertical-align:bottom" width="142" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S0195669816300063-si21.gif">script><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span>. For a con
stant <
span id="mml
si1" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si1.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=1e6227abaf358996ae54ab98f58ffbbb" title="Click to view the MathML
source">k
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span> we
show that <
span id="mml
si23" cla
ss="mathml
src">
source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0195669816300063&_mathId=si23.gif&_user=111111111&_pii=S0195669816300063&_rdoc=1&_issn=01956698&md5=239a5d070062a76567df0ee4c05b08c9">ss="imgLazyJSB inlineImage" height="24" width="151" alt="View the MathML source" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0195669816300063-si23.gif">script>style="vertical-align:bottom" width="151" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S0195669816300063-si23.gif">script><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span>. Moreover, we prove an upper bound for <
span id="mml
si13" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si13.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=1cc020038412efed175a6c7f7cbfd736" title="Click to view the MathML
source">g<
sub>k
sub>(n)
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span> that allow
s u
s to
show that <
span id="mml
si25" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si25.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=1d51d4673da94cc357067c1c9c51b934" title="Click to view the MathML
source">g<
sub>k
sub>(n)=n(1+o(1))
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span> for every <
span id="mml
si16" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si16.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=c7548b87a6a545e246719d1562d91366" title="Click to view the MathML
source">k=⌊cn<
sup>α
sup>⌋
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span>, where <
span id="mml
si19" cla
ss="mathml
src"><
span cla
ss="formulatext
stixSupport mathImg" data-mathURL="/
science?_ob=MathURL&_method=retrieve&_eid=1-
s2.0-S0195669816300063&_mathId=
si19.gif&_u
ser=111111111&_pii=S0195669816300063&_rdoc=1&_i
ssn=01956698&md5=9e87bcf4fd9232111b181392172644c9" title="Click to view the MathML
source">c>0
span><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span> and <
span id="mml
si28" cla
ss="mathml
src">
source" class="mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0195669816300063&_mathId=si28.gif&_user=111111111&_pii=S0195669816300063&_rdoc=1&_issn=01956698&md5=37dd6520eb4b35123c357111ab94e44e">ss="imgLazyJSB inlineImage" height="21" width="71" alt="View the MathML source" title="View the MathML source" src="/sd/grey_pxl.gif" data-inlimgeid="1-s2.0-S0195669816300063-si28.gif">script>style="vertical-align:bottom" width="71" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S0195669816300063-si28.gif">script><
span cla
ss="mathContainer hidden"><
span cla
ss="mathCode">
span>
span>
span>.