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 A206721 #7 Mar 30 2012 18:37:35
%S A206721 1,1,1,2,5,12,28,65,155,387,1002,2641,7016,18743,50321,135608,366399,
%T A206721 992221,2693705,7333666,20026582,54858122,150739957,415479332,
%U A206721 1148563576,3183963911,8848963329,24650364462,68810859415,192439812663,539072534278,1512285566266
%N A206721 G.f.: A(x) = ...o x/(1-x^7) o x/(1-x^5) o x/(1-x^3) o x/(1-x), a composition of functions x/(1-x^(2*n-1)) for n=...3,2,1.
%C A206721 Compositional transpose of A206720.
%e A206721 G.f.: A(x) = x + x^2 + x^3 + 2*x^4 + 5*x^5 + 12*x^6 + 28*x^7 + 65*x^8 +...
%e A206721 where A(x) is the limit of composition of functions x/(1-x^(2*n-1)):
%e A206721 F_1(x) = x/(1-x)
%e A206721 F_2(x) = x/(1-x^3) o F_1(x) = x + x^2 + x^3 + 2*x^4 + 5*x^5 + 11*x^6 +...
%e A206721 F_3(x) = x/(1-x^5) o F_2(x) = x + x^2 + x^3 + 2*x^4 + 5*x^5 + 12*x^6 +...
%e A206721 F_4(x) = x/(1-x^7) o x/(1-x^5) o x/(1-x^3) o x/(1-x); ...
%o A206721 (PARI) {a(n)=local(A=x+x*O(x^n)); if(n<=0, 0, for(i=1, n, A=A/(1-A^(2*i-1))); polcoeff(A, n))}
%o A206721 for(n=1,45,print1(a(n),", "))
%Y A206721 Cf. A206720, A136751.
%K A206721 nonn
%O A206721 1,4
%A A206721 _Paul D. Hanna_, Feb 11 2012