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 A209558 #5 Mar 30 2012 18:58:15 %S A209558 1,2,2,2,5,4,3,7,11,8,3,13,21,23,16,4,15,44,57,47,32,4,24,60,129,145, %T A209558 95,64,5,26,108,207,346,353,191,128,5,38,130,405,646,875,833,383,256, %U A209558 6,40,212,545,1345,1877,2124,1921,767,512,6,55,240,965,2021 %N A209558 Triangle of coefficients of polynomials v(n,x) jointly generated with A209557; see the Formula section. %C A209558 For a discussion and guide to related arrays, see A208510. %F A209558 u(n,x)=x*u(n-1,x)+v(n-1,x), %F A209558 v(n,x)=u(n-1,x)+2x*v(n-1,x)+1, %F A209558 where u(1,x)=1, v(1,x)=1. %e A209558 First five rows: %e A209558 1 %e A209558 2...2 %e A209558 2...5...4 %e A209558 3...7...11...8 %e A209558 3...13...21...23...16 %e A209558 First three polynomials v(n,x): 1, 2 + 2x , 2+ 5x + 4x^2 . %t A209558 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A209558 u[n_, x_] := x*u[n - 1, x] + v[n - 1, x]; %t A209558 v[n_, x_] := u[n - 1, x] + 2 x*v[n - 1, x] + 1; %t A209558 Table[Expand[u[n, x]], {n, 1, z/2}] %t A209558 Table[Expand[v[n, x]], {n, 1, z/2}] %t A209558 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A209558 TableForm[cu] %t A209558 Flatten[%] (* A209557 *) %t A209558 Table[Expand[v[n, x]], {n, 1, z}] %t A209558 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A209558 TableForm[cv] %t A209558 Flatten[%] (* A209558 *) %Y A209558 Cf. A209557, A208510. %K A209558 nonn,tabl %O A209558 1,2 %A A209558 _Clark Kimberling_, Mar 10 2012