This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A156731 #4 Jan 03 2014 15:51:37 %S A156731 0,0,1,0,1,0,0,0,0,1,0,1,0,0,1,0,1,0,0,0,1,0,1,0,1,0,0,0,0,1,0,1,0,0, %T A156731 0,1,0,1,0,0,1,0,0,1,0,0,0,1,0,0,1,0,1,0,0,0,1,0,1,0,0,0,0,1,0,1,0,0, %U A156731 0,0,1,0,1,0,0,1,0,1,0,0,0,1,0,0,1,0,1,0,0,0,1,0,1,0,0,1,0,1,0,1,0,0,0,0,1 %N A156731 a(n)=(v(2*n+1)-v(2*n-1))/2 where v(n)=A156253(n)-A156251(n). %Y A156731 Cf. A054354 %K A156731 nonn %O A156731 1,1 %A A156731 _Benoit Cloitre_, Feb 14 2009