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 A209701 #5 Mar 30 2012 18:58:15 %S A209701 1,0,2,0,2,5,0,3,7,12,0,4,11,23,29,0,5,16,41,70,70,0,6,22,66,140,204, %T A209701 169,0,7,29,99,247,455,577,408,0,8,37,141,401,875,1423,1597,985,0,9, %U A209701 46,193,613,1529,2965,4321,4348,2378,0,10,56,256,895,2495,5549 %N A209701 Triangle of coefficients of polynomials u(n,x) jointly generated with A209702; see the Formula section. %C A209701 For a discussion and guide to related arrays, see A208510. %F A209701 u(n,x)=x*u(n-1,x)+x*v(n-1,x), %F A209701 v(n,x)=2x*u(n-1,x)+(x+1)v(n-1,x)+1, %F A209701 where u(1,x)=1, v(1,x)=1. %e A209701 First five rows: %e A209701 1 %e A209701 0...2 %e A209701 0...2...5 %e A209701 0...3...7....12 %e A209701 0...4...11...23...29 %e A209701 First three polynomials v(n,x): 1, 2x, 2x + 5x^2. %t A209701 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A209701 u[n_, x_] := x*u[n - 1, x] + x*v[n - 1, x]; %t A209701 v[n_, x_] := 2 x*u[n - 1, x] + (x + 1)*v[n - 1, x] + 1; %t A209701 Table[Expand[u[n, x]], {n, 1, z/2}] %t A209701 Table[Expand[v[n, x]], {n, 1, z/2}] %t A209701 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A209701 TableForm[cu] %t A209701 Flatten[%] (* A209701 *) %t A209701 Table[Expand[v[n, x]], {n, 1, z}] %t A209701 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A209701 TableForm[cv] %t A209701 Flatten[%] (* A209702 *) %Y A209701 Cf. A209702, A208510. %K A209701 nonn,tabl %O A209701 1,3 %A A209701 _Clark Kimberling_, Mar 12 2012