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 A193199 #12 Jul 02 2022 09:27:36
%S A193199 1,1,5,49,1025,42241,3610625,609251329,210923290625,144320565411841,
%T A193199 201501092228890625,556475188311619534849,3125896980250691972890625,
%U A193199 34751531654955460673195212801,784223845648499469575195012890625
%N A193199 G.f.: A(x) = Sum_{n>=0} x^n/(1 - 4^n*x)^n.
%H A193199 Seiichi Manyama, <a href="/A193199/b193199.txt">Table of n, a(n) for n = 0..80</a>
%F A193199 a(n) = Sum_{k=0..n-1} binomial(n-1,k)*4^(k*(n-k)) for n>0 with a(0)=1.
%e A193199 G.f.: A(x) = 1 + x + 5*x^2 + 49*x^3 + 1025*x^4 + 42241*x^5 +...
%e A193199 where:
%e A193199 A(x) = 1 + x/(1-4*x) + x^2/(1-16*x)^2 + x^3/(1-64*x)^3 + x^4/(1-256*x)^4 +...
%o A193199 (PARI) {a(n)=local(A=1);A=1+sum(m=1,n,x^m/(1-4^m*x +x*O(x^n))^m);polcoeff(A,n)}
%o A193199 (PARI) {a(n)=if(n==0,1,sum(k=0,n-1,binomial(n-1,k)*4^(k*(n-k))))}
%Y A193199 Cf. A000684, A193198.
%K A193199 nonn
%O A193199 0,3
%A A193199 _Paul D. Hanna_, Jul 17 2011