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 A209570 #8 Mar 30 2012 18:58:15 %S A209570 1,2,2,3,4,2,4,8,8,2,5,14,20,12,2,6,22,42,40,16,2,7,32,78,102,68,20,2, %T A209570 8,44,132,222,210,104,24,2,9,58,208,432,534,382,148,28,2,10,74,310, %U A209570 772,1188,1126,634,200,32,2,11,92,442,1290,2392,2848,2142,982 %N A209570 Triangle of coefficients of polynomials v(n,x) jointly generated with A209569; see the Formula section. %C A209570 For n>1, row n begins and ends with 2. %C A209570 Alternating row sums: 1,0,1,2,1,0,1,2,1,0,1,2,... %C A209570 For a discussion and guide to related arrays, see A208510. %F A209570 u(n,x)=x*u(n-1,x)+v(n-1,x), %F A209570 v(n,x)=2x*u(n-1,x)+v(n-1,x) +1, %F A209570 where u(1,x)=1, v(1,x)=1. %e A209570 First five rows: %e A209570 1 %e A209570 2...2 %e A209570 3...4....2 %e A209570 4...8....8....2 %e A209570 5...14...20...12...2 %e A209570 First three polynomials v(n,x): 1, 2 + 2x , 3 + 4x + 2x^2. %t A209570 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A209570 u[n_, x_] := x*u[n - 1, x] + v[n - 1, x]; %t A209570 v[n_, x_] := 2 x*u[n - 1, x] + v[n - 1, x] + 1; %t A209570 Table[Expand[u[n, x]], {n, 1, z/2}] %t A209570 Table[Expand[v[n, x]], {n, 1, z/2}] %t A209570 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A209570 TableForm[cu] %t A209570 Flatten[%] (* A209569 *) %t A209570 Table[Expand[v[n, x]], {n, 1, z}] %t A209570 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A209570 TableForm[cv] %t A209570 Flatten[%] (* A209570 *) %Y A209570 Cf. A209569, A208510. %K A209570 nonn,tabl %O A209570 1,2 %A A209570 _Clark Kimberling_, Mar 10 2012