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 A248656 #9 Oct 30 2014 17:14:33
%S A248656 1,-4,1172,-2394604,17925470132,-356711164156204,15557257046545589492,
%T A248656 -1306859934761006954164204,192757826813283097789632563252,
%U A248656 -46564510721452609888686654192978604,17449940281041871638688960825766828695412,-9712709908164237387647891995373875626734039404
%N A248656 E.g.f.: Sum_{n>=0} exp(n*(n+1)/2*x) / (1 + exp(n*x))^(n+1) = Sum_{n>=0} a(n) * x^(2*n) / (2*n)!.
%C A248656 Compare to an e.g.f. of A122399: Sum_{n>=0} exp(n^2*x)/(1 + exp(n*x))^(n+1).
%e A248656 E.g.f.: A(x) = 1 - 4*x^2/2! + 1172*x^4/4! - 2394604*x^6/6! + 17925470132*x^8/8! -+...
%e A248656 where
%e A248656 A(x) = 1/2 + exp(x)/(1+exp(x))^2 + exp(3*x)/(1+exp(2*x))^3 + exp(6*x)/(1+exp(3*x))^4 + exp(10*x)/(1+exp(4*x))^5 + exp(15*x)/(1+exp(5*x))^6 + exp(21*x)/(1+exp(6*x))^7 +...
%o A248656 (PARI) \p100 \\ set precision
%o A248656 {A=Vec(serlaplace(sum(n=0,800,1.*exp((n^2+n)/2*x +O(x^31))/(1 + exp(n*x +O(x^31)))^(n+1)) ))}
%o A248656 for(n=1,#A\2,print1(round(A[2*n-1]),", "))
%Y A248656 Cf. A122399, A248657.
%K A248656 sign
%O A248656 0,2
%A A248656 _Paul D. Hanna_, Oct 26 2014