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 A115399 #4 Feb 20 2015 18:03:21
%S A115399 1,0,-1,1,2,-4,-3,15,-1,-51,42,154,-274,-372,1341,405,-5599,2783,
%T A115399 20295,-27313,-61139,160797,124462,-767702,94964,3145986,-2930086,
%U A115399 -10956466,21290868,29513156,-114974111,-33473459,522016279,-279684579,-2031228003,2867285041,6493289367,-17791297065
%N A115399 Expansion of c(x^2-x^3), c(x) the g.f. of A000108.
%C A115399 Diagonal sums of A115179.
%F A115399 a(n)=sum{k=0..floor(n/2), (-1)^(n-k)*C(k)C(k,n-2k)}.
%F A115399 Conjecture: (n+2)*a(n) +(-n-2)*a(n-1) +4*(n-1)*a(n-2) +2*(-4*n+7)*a(n-3) +2*(2*n-5)*a(n-4)=0. - _R. J. Mathar_, Feb 20 2015
%Y A115399 Cf. A115178.
%K A115399 easy,sign
%O A115399 0,5
%A A115399 _Paul Barry_, Mar 14 2006