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 A056590 #4 Mar 31 2012 13:20:04 %S A056590 1,7,53,318,1784,9288,46233,221859,1036585,4742650,21350264,94895016, %T A056590 417562385,1822824255,7907350365,34130697462,146735898760, %U A056590 628870859320,2688466352825,11470754475675,48865641344081,207913415718642 %N A056590 Fourth column sequence of triangle A056588. %F A056590 a(n)= A056588(n+3, 3), n >= 0. %F A056590 a(n)= 3^(n+4)-F(n+5)*2^(n+4)+(F(n+3)-2)*F(n+5)*F(n+4)/2; F(n)=A000045(n) (Fibonacci). %F A056590 G.f.:(1-3*x+8*x^2-3*x^3-3*x^4-4*x^5)/((1+x)*(1-3*x)*(1+x-x^2)*(1-2*x-4*x^2)*(1-3*x+x^2)*(1-4*x-x^2)). %Y A056590 Cf. A000045, A056588, A000012, A000071, A056589. %K A056590 nonn,easy %O A056590 0,2 %A A056590 _Wolfdieter Lang_ Jul 10 2000