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 A112123 #6 Mar 14 2015 00:56:21
%S A112123 1,1,-9,131,-2279,43161,-849269,16866851,-331093879,6316647841,
%T A112123 -115528321709,2007845708091,-33238536213650,537616162919975,
%U A112123 -8956186512464320,158920634214746905,-2786226293720310297,38547971903938600271,-198392033014273765511
%N A112123 G.f. A(x) satisfies A(A(A(..(A(x))..))) = B(x) (11th self-COMPOSE of A) such that the coefficients of B(x) consist only of numbers {1,2,3,..,11}, with B(0) = 0.
%e A112123 A(x) = x + x^2 - 9*x^3 + 131*x^4 - 2279*x^5 + 43161*x^6 - 849269*x^7 +...
%e A112123 where A(A(A(A(A(A(A(A(A(A(A(x))))))))))) =
%e A112123 x + 11*x^2 + 11*x^3 + 11*x^4 + 11*x^5 + 11*x^6 + 11*x^7 +...
%e A112123 is the g.f. of A112122.
%o A112123 (PARI) {a(n,m=11)=local(F=x+x^2+x*O(x^n),G);if(n<1,0, for(k=3,n, G=F+x*O(x^k);for(i=1,m-1,G=subst(F,x,G)); F=F-((polcoeff(G,k)-1)\m)*x^k); return(polcoeff(F,n,x)))}
%Y A112123 Cf. A112122, A112104-A112121, A112124-A112127.
%K A112123 sign
%O A112123 1,3
%A A112123 _Paul D. Hanna_, Aug 27 2005