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 A055250 #14 Sep 20 2017 07:44:22
%S A055250 1,9,47,187,630,1898,5282,13866,34831,84575,199977,462973,1053804,
%T A055250 2365704,5250660,11543700,25177005,54539205,117456115,251676495,
%U A055250 536892146,1140875254,2415947382,5100306062,10737455195,22548620283
%N A055250 Seventh column of triangle A055249.
%F A055250 G.f.: 1/(((1-2*x)^2)*(1-x)^5).
%F A055250 a(n) = A055249(n+6, 6).
%F A055250 For n >= 1, a(n) = A035038(n+6) + Sum_{j=0..n-1} a(j).
%F A055250 a(n) = Sum_{k=0..n+5} Sum_{i=0..n+5} (i-k) * C(n-k+5,i+3). - _Wesley Ivan Hurt_, Sep 19 2017
%p A055250 a:= n-> (Matrix(7, (i,j)-> if (i=j-1) then 1 elif j=1 then [9,-34,70,-85,61,-24,4][i] else 0 fi)^(n))[1,1]: seq(a(n), n=0..25); # _Alois P. Heinz_, Aug 05 2008
%t A055250 Table[Sum[(-1)^(n - k) k (-1)^(n - k) Binomial[n + 5, k + 5], {k, 0, n}], {n, 1, 26}] (* _Zerinvary Lajos_, Jul 08 2009 *)
%Y A055250 Cf. A055249, A035038, partial sums of A034009.
%K A055250 easy,nonn
%O A055250 0,2
%A A055250 _Wolfdieter Lang_, May 26 2000