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 A261401 #14 Dec 19 2015 14:20:12
%S A261401 1,1,0,-2,1,3,-2,-4,1,6,0,-8,2,8,-4,-10,3,15,-2,-16,4,16,-8,-22,7,28,
%T A261401 -2,-30,7,33,-14,-40,9,48,-8,-54,16,60,-20,-68,19,82,-16,-94,21,98,
%U A261401 -34,-116,32,138,-24,-146,40,165,-54,-190,45,212,-46,-240
%N A261401 Expansion of 1 + Sum_{n>=1} ( q^(n^2)/Product_{i=1..n} ((1+q^(2*i))^2) ).
%p A261401 phi:=1+add( q^(n^2)/mul((1+q^(2*i))^2,i=1..n), n=1..61):
%p A261401 series(phi,q,60);
%p A261401 seriestolist(%);
%Y A261401 Suggested by the g.f.'s for A000025 and A053250.
%K A261401 sign
%O A261401 0,4
%A A261401 _N. J. A. Sloane_, Aug 20 2015