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 A218669 #4 Nov 04 2012 15:05:55 %S A218669 1,0,1,7,97,1561,41136,1551814,72440460,4281320257,324623105584, %T A218669 30086950057627,3299720918091511,428431079916572044, %U A218669 65637957066642609845,11659659637028895337265,2367270866164121777222596,546795407830461739380895161,143176487805296033192642234802 %N A218669 O.g.f.: Sum_{n>=0} 1/(1-n^3*x)^n * x^n/n! * exp(-x/(1-n^3*x)). %C A218669 Compare g.f. to the curious identity: %C A218669 1/(1-x^2) = Sum_{n>=0} (1+n*x)^n * x^n/n! * exp(-x*(1+n*x)). %e A218669 O.g.f.: A(x) = 1 + x^2 + 7*x^3 + 97*x^4 + 1561*x^5 + 41136*x^6 +... %e A218669 where %e A218669 A(x) = exp(-x) + x/(1-x)*exp(-x/(1-x)) + x^2/(1-8*x)^2/2!*exp(-x/(1-8*x)) + x^3/(1-27*x)^3/3!*exp(-x/(1-27*x)) + x^4/(1-64*x)^4/4!*exp(-x/(1-64*x)) + x^5/(1-125*x)^5/5!*exp(-x/(1-125*x)) +... %e A218669 simplifies to a power series in x with integer coefficients. %o A218669 (PARI) {a(n)=local(A=1+x,X=x+x*O(x^n));A=sum(k=0,n,1/(1-k^3*X)^k*x^k/k!*exp(-X/(1-k^3*X)));polcoeff(A,n)} %o A218669 for(n=0,30,print1(a(n),", ")) %Y A218669 Cf. A218667, A218668, A218670, A217900. %K A218669 nonn %O A218669 0,4 %A A218669 _Paul D. Hanna_, Nov 04 2012