With α irrational the graph of [jα] against
integer j, displays interesting patterns of self-matching. This is best seen by comparing the
Bernoulli (characteristic Sturmian) or difference sequence β
j, term by term with the Bernoulli sequence displaced by k terms β
j−k, where
βj=[(j+1)α]−[jα].It is shown that the fraction of such self-matching is the surprisingly simple M(k)=max(1−2{α},1−2{kα}).Of particular interest is the graph of M(k) against k as it is seen to exhibit an unexpected Moiré pattern obtained simply by folding the lower half of the graph of {kα} over the upper half.