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 A209772 #5 Mar 30 2012 18:58:15 %S A209772 1,2,2,2,5,4,3,9,14,8,3,14,32,36,16,4,20,60,100,88,32,4,27,100,220, %T A209772 288,208,64,5,35,154,420,728,784,480,128,5,44,224,728,1568,2240,2048, %U A209772 1088,256,6,54,312,1176,3024,5376,6528,5184,2432,512,6,65,420 %N A209772 Triangle of coefficients of polynomials v(n,x) jointly generated with A209771; see the Formula section. %C A209772 Alternating row sums: 1,0,1,0,1,0,1,0,... %C A209772 For a discussion and guide to related arrays, see A208510. %F A209772 u(n,x)=x*u(n-1,x)+(x+1)*v(n-1,x), %F A209772 v(n,x)=(x+1)*u(n-1,x)+x*v(n-1,x)+1, %F A209772 where u(1,x)=1, v(1,x)=1. %e A209772 First five rows: %e A209772 1 %e A209772 2...2 %e A209772 2...5....4 %e A209772 3...9....14...8 %e A209772 3...14...32...36...16 %e A209772 First three polynomials v(n,x): 1, 2 + 2x , 2 + 5x + 4x^2. %t A209772 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A209772 u[n_, x_] := x*u[n - 1, x] + (x + 1)*v[n - 1, x]; %t A209772 v[n_, x_] := (x + 1)*u[n - 1, x] + x*v[n - 1, x] + 1; %t A209772 Table[Expand[u[n, x]], {n, 1, z/2}] %t A209772 Table[Expand[v[n, x]], {n, 1, z/2}] %t A209772 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A209772 TableForm[cu] %t A209772 Flatten[%] (* A209771 *) %t A209772 Table[Expand[v[n, x]], {n, 1, z}] %t A209772 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A209772 TableForm[cv] %t A209772 Flatten[%] (* A209772 *) %Y A209772 Cf. A209671, A208510. %K A209772 nonn,tabl %O A209772 1,2 %A A209772 _Clark Kimberling_, Mar 15 2012