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 A209702 #5 Mar 30 2012 18:58:15 %S A209702 1,2,3,3,5,7,4,8,16,17,5,12,30,47,41,6,17,50,99,134,99,7,23,77,181, %T A209702 315,373,239,8,30,112,302,628,968,1020,577,9,38,156,472,1128,2090, %U A209702 2898,2751,1393,10,47,210,702,1882,4020,6738,8495,7338,3363,11,57 %N A209702 Triangle of coefficients of polynomials v(n,x) jointly generated with A209701; see the Formula section. %C A209702 For a discussion and guide to related arrays, see A208510. %F A209702 u(n,x)=x*u(n-1,x)+x*v(n-1,x), %F A209702 v(n,x)=2x*u(n-1,x)+(x+1)v(n-1,x)+1, %F A209702 where u(1,x)=1, v(1,x)=1. %e A209702 First five rows: %e A209702 1 %e A209702 2...3 %e A209702 3...5....7 %e A209702 4...8....16...17 %e A209702 5...12...30...57...41 %e A209702 First three polynomials v(n,x): 1, 2 + 3x , 3 + 5x + 7x^2. %t A209702 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A209702 u[n_, x_] := x*u[n - 1, x] + x*v[n - 1, x]; %t A209702 v[n_, x_] := 2 x*u[n - 1, x] + (x + 1)*v[n - 1, x] + 1; %t A209702 Table[Expand[u[n, x]], {n, 1, z/2}] %t A209702 Table[Expand[v[n, x]], {n, 1, z/2}] %t A209702 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A209702 TableForm[cu] %t A209702 Flatten[%] (* A209701 *) %t A209702 Table[Expand[v[n, x]], {n, 1, z}] %t A209702 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A209702 TableForm[cv] %t A209702 Flatten[%] (* A209702 *) %Y A209702 Cf. A209701, A208510. %K A209702 nonn,tabl %O A209702 1,2 %A A209702 _Clark Kimberling_, Mar 12 2012