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 A167683 #4 Aug 10 2015 00:28:51 %S A167683 1,0,-1,1,0,0,-1,0,1,0,0,0,1,0,0,1,0,0,0,0,1,0,0,0,1,0,0,0,0,0,-1,0,0, %T A167683 0,0,1,0,0,0,0,0,0,-1,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,1,0,0,0, %U A167683 0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,-1,0,0,0,0,0,0,0,0,1,0,0,0,0 %N A167683 Hankel transform of A007325. %C A167683 Nonzero elements appear to be indexed by abs(A131723). -1 elements appear to be indexed by 2*A014493(n). %K A167683 sign %O A167683 0,1 %A A167683 _Paul Barry_, Nov 09 2009