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 A118410 #3 Mar 30 2012 18:36:57
%S A118410 1,1,3,21,321,10385,699073,96908737,27478721537,15863659383041,
%T A118410 18583701166494721,44066148876930001921,211105432749968736673793,
%U A118410 2040201553888722742048509953,39729701298130761785818052935681
%N A118410 G.f. A(x) = Sum_{n>=0} a(n)*x^n/2^(n*(n-1)/2) satisfies: A(x) = Sum_{n>=0} A(x)^n*x^n/2^(n*(n-1)/2).
%F A118410 G.f.: A(x) = (1/x)*series_reversion[x/Sum_{n>=0} x^n/2^(n*(n-1)/2)].
%e A118410 A(x) = 1 + x + 3*x^2/2 + 21*x^3/8 + 321*x^4/64 + 10385*x^5/1024 +...
%e A118410 A(x) = 1 + x*A(x) + x^2*A(x)^2/2 + x^3*A(x)^3/8 +...
%o A118410 (PARI) {a(n)=2^(n*(n-1)/2)*polcoeff(1/x*serreverse(x/sum(k=0,n,x^k/2^(k*(k-1)/2)+x*O(x^n))),n)}
%Y A118410 Cf. A117401.
%K A118410 nonn
%O A118410 0,3
%A A118410 _Paul D. Hanna_, Apr 27 2006