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 A295518 #7 Dec 18 2017 04:15:17
%S A295518 0,1,4,14,52,220,1092,6388,43588,341444,3022660,29835844,324782916,
%T A295518 3864151876,49875956548,694041238340,10356520497988,164956188717892,
%U A295518 2793150548587332,50100649026499396,948943120107352900,18925792541725471556,396439630395708060484
%N A295518 a(n) = e^2 * Sum_{k=0..n-1} Gamma(k + 1, 2).
%F A295518 a(n) = (2*n-4)*a(n-3)+(3-3*n)*a(n-2)+(2+n)*a(n-1) for n >= 3.
%p A295518 a := proc(n) option remember; if n=0 then 0 elif n=1 then 1 elif n=2 then 4 else
%p A295518 (2*n-4)*a(n-3)+(3-3*n)*a(n-2)+(2+n)*a(n-1) fi end: seq(a(n), n=0..22);
%t A295518 a[n_] := E^2 Sum[Gamma[k + 1, 2], {k,0,n-1}]; Table[a[n], {n,0,22}]
%Y A295518 Cf. A010842.
%K A295518 nonn
%O A295518 0,3
%A A295518 _Peter Luschny_, Dec 17 2017