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 A138210 #2 Mar 30 2012 18:37:09
%S A138210 1,1,-2,11,-96,1137,-16972,305653,-6449876,156135481,-4266372138,
%T A138210 129918213186,-4363433172488,160251326396727,-6389255111157990,
%U A138210 274851082201092530,-12689236310679318864,625827924636908620381,-32839089116018960634852
%N A138210 G.f.: A(x) = 1 + x*(1 + x*(1 + x*(...(1 + x*(...)^(-2n) )...)^-6)^-4)^-2.
%e A138210 G.f.: A(x)=1+x/B(x)^2, B(x)=1+x/C(x)^4, C(x)=1+x/D(x)^6, D(x)=1+x/E(x)^8,...
%e A138210 where A(x),B(x),C(x),... are the g.f. of the sequences given below.
%e A138210 A=[1,1,-2,11,-96,1137,-16972,305653,-6449876,156135481,...];
%e A138210 B=[1,1,-4,34,-416,6487,-121740,2660394,-66258116,1852007663,...];
%e A138210 C=[1,1,-6,69,-1088,21126,-480360,12432418,-359714328,11490821943,...];
%e A138210 D=[1,1,-8,116,-2240,52130,-1395592,41877192,-1385795096,50020840015,...];
%e A138210 E=[1,1,-10,175,-4000,108575,-3348372,114475615,-4273407500,...];
%e A138210 F=[1,1,-12,246,-6496,201537,-7039284,270347826,-11252124732,...]; ...
%o A138210 (PARI) {a(n)=local(A=1+x+x*O(x^n)); for(j=0, n-1, A=1+x*A^(-2*(n-j))); polcoeff(A, n)}
%Y A138210 Cf. A121587, A138212, A138209, A138208.
%K A138210 sign
%O A138210 0,3
%A A138210 _Paul D. Hanna_, Mar 06 2008