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 A117415 #11 Apr 27 2023 09:55:05
%S A117415 0,0,1,12,272,9920,530688,39144448,3807514624,472197021696,
%T A117415 72722212782080,13616619646091264,3046271659520557056,
%U A117415 802494810618175946752,245880605613803859607552,86696940704285991905525760,34855851028500677184683245568
%N A117415 E.g.f. (x*tan(x)-x^2)/8 (even powers only).
%F A117415 a(n) = 2^(2*n-1) * (2^(2*n)-1) * abs(Bernoulli(2*n))/4 - (C(1,n) - C(0,n))/4.
%t A117415 With[{nn=40},Take[CoefficientList[Series[(x*Tan[x]-x^2)/8,{x,0,nn}],x] Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, May 06 2014 *)
%Y A117415 Column k=2 of Euler triangle A117414.
%K A117415 easy,nonn
%O A117415 0,4
%A A117415 _Paul Barry_, Mar 13 2006
%E A117415 More terms from _Harvey P. Dale_, May 06 2014