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 A121587 #3 Mar 30 2012 18:36:58
%S A121587 1,1,-1,3,-14,87,-672,6202,-66622,817205,-11278833,173092010,
%T A121587 -2925096344,53989582136,-1080876094507,23331975207984,
%U A121587 -540247838958615,13357882578863941,-351281262266717583,9790602495326179971,-288289868480192337409,8942994568771904297378
%N A121587 G.f.: A(x) = 1+x*(1+x*(1+x*(...(1+x*(...)^(-n) )...)^-3)^-2)^-1.
%e A121587 G.f.: A(x) = 1 + x/B(x); B(x) = 1 + x/C(x)^2; C(x) = 1 + x/D(x)^3;
%e A121587 D(x) = 1 + x/E(x)^4; E(x) = 1 + x/F(x)^5; ...
%e A121587 where the respective sequences begin:
%e A121587 B=[1,1,-2,9,-58,472,-4584,51481,-655244,9318663,...];
%e A121587 C=[1,1,-3,18,-148,1491,-17496,232556,-3441024,56009937,...];
%e A121587 D=[1,1,-4,30,-300,3605,-49656,763968,-12920820,237676330,...];
%e A121587 E=[1,1,-5,45,-530,7400,-117096,2048865,-39048150,802555995,...];
%e A121587 F=[1,1,-6,63,-854,13587,-242928,4766594,-101163336,...].
%o A121587 (PARI) {a(n)=local(A=1+x+x*O(x^n)); for(j=0, n-1, A=1+x/A^(n-j)); polcoeff(A, n)}
%Y A121587 Cf. A095793 (variant).
%K A121587 sign
%O A121587 0,4
%A A121587 _Paul D. Hanna_, Aug 09 2006