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 A218687 #7 Nov 05 2012 18:48:33
%S A218687 1,1,2,31,398,10476,296407,12613297,592445192,36797742660,
%T A218687 2524966492661,212912151736648,19819138754732997,2155966497948737905,
%U A218687 259256365067737582615,35050667748654756208069,5257919606219599751747894,858816581875175776426876930
%N A218687 O.g.f.: Sum_{n>=0} n^n * (1+n^3*x)^n * x^n/n! * exp(-n*(1+n^3*x)*x).
%C A218687 Compare the o.g.f. to the curious identity:
%C A218687 1/(1-x^2) = Sum_{n>=0} (1+n*x)^n * x^n/n! * exp(-(1+n*x)*x).
%e A218687 O.g.f: A(x) = 1 + x + 2*x^2 + 31*x^3 + 398*x^4 + 10476*x^5 + 296407*x^6 +...
%e A218687 where
%e A218687 A(x) = 1 + (1+x)*x*exp(-(1+x)*x) + 2^2*(1+2^3*x)^2*x^2/2!*exp(-2*(1+2^3*x)*x) + 3^3*(1+3^3*x)^3*x^3/3!*exp(-3*(1+3^3*x)*x) + 4^4*(1+4^3*x)^4*x^4/4!*exp(-4*(1+4^3*x)*x) + 5^5*(1+5^3*x)^5*x^5/5!*exp(-5*(1+5^3*x)*x) +...
%e A218687 simplifies to a power series in x with integer coefficients.
%o A218687 (PARI) {a(n)=polcoeff(sum(k=0,n,k^k*(1+k^3*x)^k*x^k/k!*exp(-k*x*(1+k^3*x)+x*O(x^n))),n)}
%o A218687 for(n=0,30,print1(a(n),", "))
%Y A218687 Cf. A218685, A218686, A218684.
%K A218687 nonn
%O A218687 0,3
%A A218687 _Paul D. Hanna_, Nov 05 2012