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 A209698 #5 Mar 30 2012 18:58:15 %S A209698 1,2,2,3,4,4,4,7,10,8,5,11,20,24,16,6,16,35,54,56,32,7,22,56,104,140, %T A209698 128,64,8,29,84,181,294,352,288,128,9,37,120,293,552,800,864,640,256, %U A209698 10,46,165,449,957,1610,2112,2080,1408,512,11,56,220,659,1562 %N A209698 Triangle of coefficients of polynomials v(n,x) jointly generated with A209697; see the Formula section. %C A209698 For a discussion and guide to related arrays, see A208510. %F A209698 u(n,x)=x*u(n-1,x)+x*v(n-1,x), %F A209698 v(n,x)=x*u(n-1,x)+(x+1)*v(n-1,x)+1, %F A209698 where u(1,x)=1, v(1,x)=1. %e A209698 First five rows: %e A209698 1 %e A209698 2...2 %e A209698 3...4....4 %e A209698 4...7....10...8 %e A209698 5...11...20...24...16 %e A209698 First three polynomials v(n,x): 1, 2 + 2x , 3 + 4x + 4x^2. %t A209698 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A209698 u[n_, x_] := x*u[n - 1, x] + x*v[n - 1, x]; %t A209698 v[n_, x_] := x*u[n - 1, x] + (x + 1)*v[n - 1, x] + 1; %t A209698 Table[Expand[u[n, x]], {n, 1, z/2}] %t A209698 Table[Expand[v[n, x]], {n, 1, z/2}] %t A209698 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A209698 TableForm[cu] %t A209698 Flatten[%] (* A209697 *) %t A209698 Table[Expand[v[n, x]], {n, 1, z}] %t A209698 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A209698 TableForm[cv] %t A209698 Flatten[%] (* A209698 *) %Y A209698 Cf. A209697, A208510. %K A209698 nonn,tabl %O A209698 1,2 %A A209698 _Clark Kimberling_, Mar 12 2012