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 A209776 #5 Mar 30 2012 18:58:15 %S A209776 1,3,2,5,8,4,9,22,22,8,15,52,78,56,16,25,112,226,242,136,32,41,228, %T A209776 580,828,692,320,64,67,446,1374,2456,2726,1872,736,128,109,848,3074, %U A209776 6612,9158,8336,4864,1664,256,177,1578,6590,16590,27564,31250 %N A209776 Triangle of coefficients of polynomials v(n,x) jointly generated with A209773; see the Formula section. %C A209776 Alternating row sums: 1,1,1,1,1,1,1,1,... %C A209776 For a discussion and guide to related arrays, see A208510. %F A209776 u(n,x)=x*u(n-1,x)+(x+1)*v(n-1,x), %F A209776 v(n,x)=(x+1)*u(n-1,x)+2x*v(n-1,x)+1, %F A209776 where u(1,x)=1, v(1,x)=1. %e A209776 First five rows: %e A209776 1 %e A209776 3....2 %e A209776 5....8....4 %e A209776 9....22...22...8 %e A209776 15...52...78...56...16 %e A209776 First three polynomials v(n,x): 1, 3 + 2x , 5 + 8x + 4x^2. %t A209776 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A209776 u[n_, x_] := x*u[n - 1, x] + (x + 1)*v[n - 1, x]; %t A209776 v[n_, x_] := (x + 1)*u[n - 1, x] + (x + 1)*v[n - 1, x] + 1; %t A209776 Table[Expand[u[n, x]], {n, 1, z/2}] %t A209776 Table[Expand[v[n, x]], {n, 1, z/2}] %t A209776 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A209776 TableForm[cu] %t A209776 Flatten[%] (* A209775 *) %t A209776 Table[Expand[v[n, x]], {n, 1, z}] %t A209776 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A209776 TableForm[cv] %t A209776 Flatten[%] (* A209776 *) %Y A209776 Cf. A209675, A208510. %K A209776 nonn,tabl %O A209776 1,2 %A A209776 _Clark Kimberling_, Mar 15 2012