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 A117505 #8 Aug 30 2019 04:09:24 %S A117505 1,2,1,2,4,3,2,4,16,13,2,4,16,80,67,2,4,16,80,448,381,2,4,16,80,448, %T A117505 2688,2307,2,4,16,80,448,2688,16896,14589,2,4,16,80,448,2688,16896, %U A117505 109824,95235,2,4,16,80,448,2688 %N A117505 Triangle of coefficients for polynomials used for the column g.f.s of triangle A116880, called CM(1,2). %C A117505 The g.f. G(m,x) for column m=1,2,... of triangle A116880=CM(1,2) is x*(-sum(a(m,k)*x^(k-1),k=1..m) + sum(a(m,k)*x^k,k=0..m)*2*c(2*x))/(1+x), with the o.g.f. c(x) of A000108 (Catalan numbers). %H A117505 W. Lang: <a href="/A117505/a117505.txt">First 10 rows.</a> %F A117505 a(m,m)= A064062(m) =:C(2;m), m>=0 and a(m,k)=2*A052701(k) = C(k)*2^(k+1), for k=1,...,m-1 and C(k):=A000108(k) (Catalan). %e A117505 m=3: G(3,x)= x*(-(4+16*x+13*x^2) + %e A117505 (2+4*x+16*x^2+13*x^3)*2*c(2*x))/(1+x). %K A117505 nonn,easy,tabl %O A117505 0,2 %A A117505 _Wolfdieter Lang_, Apr 13 2006