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 A208517 #6 Mar 30 2012 18:58:13 %S A208517 1,1,3,1,3,7,1,3,8,17,1,3,9,22,41,1,3,10,27,59,99,1,3,11,32,78,157, %T A208517 239,1,3,12,37,98,222,414,577,1,3,13,42,119,294,622,1084,1393,1,3,14, %U A208517 47,141,373,864,1722,2821,3363,1,3,15,52,164,459,1141,2500,4719 %N A208517 Triangle of coefficients of polynomials v(n,x) jointly generated with A208516; see the Formula section. %F A208517 u(n,x)=u(n-1,x)+x*v(n-1,x), %F A208517 v(n,x)=x*u(n-1,x)+2x*v(n-1,x)+1, %F A208517 where u(1,x)=1, v(1,x)=1. %e A208517 First five rows: %e A208517 1 %e A208517 1...3 %e A208517 1...3...7 %e A208517 1...3...8...17 %e A208517 1...3...9...22...41 %e A208517 First five polynomials v(n,x): %e A208517 1 %e A208517 1 + 3x %e A208517 1 + 3x + 7x^2 %e A208517 1 + 3x + 8x^2 + 17x^3 %e A208517 1 + 3x + 9x^2 + 22x^3 + 41x^4 %t A208517 u[1, x_] := 1; v[1, x_] := 1; z = 16; %t A208517 u[n_, x_] := u[n - 1, x] + x*v[n - 1, x]; %t A208517 v[n_, x_] := x*u[n - 1, x] + 2 x*v[n - 1, x] + 1; %t A208517 Table[Expand[u[n, x]], {n, 1, z/2}] %t A208517 Table[Expand[v[n, x]], {n, 1, z/2}] %t A208517 cu = Table[CoefficientList[u[n, x], x], {n, 1, z}]; %t A208517 TableForm[cu] %t A208517 Flatten[%] (* A208516 *) %t A208517 Table[Expand[v[n, x]], {n, 1, z}] %t A208517 cv = Table[CoefficientList[v[n, x], x], {n, 1, z}]; %t A208517 TableForm[cv] %t A208517 Flatten[%] (* A208517 *) %Y A208517 Cf. A208514. %K A208517 nonn,tabl %O A208517 1,3 %A A208517 _Clark Kimberling_, Feb 28 2012