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 A171191 #6 Feb 03 2018 05:13:02
%S A171191 1,2,7,20,73,263,1111,4451,20161,85304,401401,1755593,8465311,
%T A171191 37866818,185756605,844627115,4196759383,19321634594,96962969047,
%U A171191 450810982796,2280344734891,10686378006479,54406554842287,256637809742444
%N A171191 G.f. satisfies: A(x) = exp( Sum_{n>=1} [A(x)^n + 1/A(-x)^n]*x^n/n ).
%F A171191 G.f. satisfies: A(x) = 1/[(1 - x*A(x))*(1 - x/A(-x))]. - _Paul D. Hanna_, Dec 06 2009
%e A171191 G.f.: A(x) = 1 + 2*x + 7*x^2 + 20*x^3 + 73*x^4 + 263*x^5 + 1111*x^6 + ...
%e A171191 log(A(x)) = [A(x)+1/A(-x)]*x + [A(x)^2+1/A(-x)^2]*x^2/2 + [A(x)^3+1/A(-x)^3]*x^3/3 + ...
%o A171191 (PARI) {a(n)=local(A=1+x+x*O(x^n));for(i=1,n,A=exp(sum(m=1,n,(A^m+subst(A^-m,x,-x)+x*O(x^n))*x^m/m)));polcoeff(A,n)}
%o A171191 (PARI) {a(n)=local(A=1+x);for(i=1,n,A=(1-x*A+x*O(x^n))^-1*(1-x/subst(A,x,-x)+x*O(x^n))^-1);polcoeff(A,n)} \\ _Paul D. Hanna_, Dec 06 2009
%Y A171191 Cf. A171190, A171199.
%K A171191 nonn
%O A171191 0,2
%A A171191 _Paul D. Hanna_, Dec 05 2009