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 A174015 #15 Sep 08 2013 19:59:26
%S A174015 1,1,2,3,4,4,2,-3,-10,-14,-4,34,104,172,132,-197,-964,-1976,-2190,652,
%T A174015 9294,23626,33762,12140,-84438,-280850,-493930,-397666,639678,3248466,
%U A174015 6947462,8068589,-2165978,-35591958,-94129444,-139864826,-56393480,352505724
%N A174015 A generalized Catalan number sequence.
%C A174015 Hankel transform is A130151(n+1). First column of A174014.
%F A174015 G.f.: (sqrt(1-2x+x^2+4x^3)+3x-1)/(2x(1-x));
%F A174015 G.f.: 1/(1-x/(1-x/(1+x/(1-x/(1-x/(1+x/(1-... (continued fraction).
%F A174015 a(n) = Sum_{k, 0<=k<=n} A091866(n,k)*(-1)^(n-k) = Sum_{k, 0<=k<=n} A198379(n,k). - _Philippe Deléham_, Nov 27 2011
%F A174015 Conjecture: (n+1)*a(n) -3*n*a(n-1) +3*(n-1)*a(n-2) +3*(n-4)*a(n-3) +2*(7-2*n)*a(n-4)=0. _R. J. Mathar_, Nov 13 2012
%K A174015 easy,sign
%O A174015 0,3
%A A174015 _Paul Barry_, Mar 05 2010
%E A174015 More terms from _Philippe Deléham_, Oct 27 2011