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 A141424 #8 Dec 16 2013 09:45:15
%S A141424 1,-3,3,-5,5,-7,7,3,-3,-121,121,1261,-1261,-20583,20583,888403,
%T A141424 -888403,-24729925,24729925,862992399,-862992399,-36913939769,
%U A141424 36913939769,1899853421885,-1899853421885,-115841483491323,115841483491323,8258802033519361
%N A141424 Numerators of second column of the inverse of the triangle of polynomial coefficients P(0,x)=1, 2P(n,x)=(1+x)*[(1+x)^(n-1)+x^(n-1)].
%C A141424 For the denominators see A053644.
%C A141424 The P(n,x) polynomials are based on the Euler polynomials and the inverse matrix of their coefficients is described in Example section of A133135. First column is A033999, third column is A133135.
%t A141424 max = 27; p[0] = 1; p[n_] := (1+x)*((1+x)^(n-1)+x^(n-1))/2; t = Table[Coefficient[p[n], x, k], {n, 0, max+2}, {k, 0, max+2}]; a[n_] := Inverse[t][[All, 2]][[n+2]] // Numerator; Table[a[n], {n, 0, max}] (* _Jean-François Alcover_, Dec 16 2013 *)
%o A141424 (PARI) lista(n) = {m = matrix(n, n); m[1, 1] = 1; for (i=2, n, pol = (1+x)*((1+x)^(i-2)+x^(i-2))/2; for (j=1, n, m[i, j] = polcoeff(pol, j-1, x););); m = 1/m; for (i=2, n, print1(numerator(m[i, 2]), ", ");); print();} \\ _Michel Marcus_, Aug 16 2013
%Y A141424 Cf. A051717.
%K A141424 sign
%O A141424 0,2
%A A141424 _Paul Curtz_, Aug 06 2008
%E A141424 Edited by _Michel Marcus_, Aug 16 2013