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 A209582 #5 Mar 30 2012 18:58:15 %S A209582 1,2,3,2,6,7,3,10,17,15,3,16,39,46,31,4,21,69,129,119,63,4,30,112,260, %T A209582 386,296,127,5,36,172,492,890,1082,713,255,5,48,242,828,1898,2832, %U A209582 2897,1674,511,6,55,342,1318,3522,6682,8511,7495,3851,1023,6,70 %N A209582 Triangle of coefficients of polynomials v(n,x) jointly generated with A209581; see the Formula section. %C A209582 For a discussion and guide to related arrays, see A208510. %F A209582 u(n,x)=x*u(n-1,x)+v(n-1,x), %F A209582 v(n,x)=(x+1)*u(n-1,x)+2x*v(n-1,x)+1, %F A209582 where u(1,x)=1, v(1,x)=1. %e A209582 First five rows: %e A209582 1 %e A209582 2...3 %e A209582 2...6....7 %e A209582 3...10...17...15 %e A209582 3...16...39...46...31 %e A209582 First three polynomials v(n,x): 1, 2 + 3x , 2 + 6x + 7x^2. %t A209582 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A209582 u[n_, x_] := x*u[n - 1, x] + v[n - 1, x]; %t A209582 v[n_, x_] := (x + 1)*u[n - 1, x] + 2 x*v[n - 1, x] + 1; %t A209582 Table[Expand[u[n, x]], {n, 1, z/2}] %t A209582 Table[Expand[v[n, x]], {n, 1, z/2}] %t A209582 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A209582 TableForm[cu] %t A209582 Flatten[%] (* A209581 *) %t A209582 Table[Expand[v[n, x]], {n, 1, z}] %t A209582 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A209582 TableForm[cv] %t A209582 Flatten[%] (* A209582 *) %Y A209582 Cf. A209581, A208510. %K A209582 nonn,tabl %O A209582 1,2 %A A209582 _Clark Kimberling_, Mar 11 2012