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 A294039 #11 Nov 15 2017 03:29:03
%S A294039 2,16,326,13700,986410,108505112,16926797486,3554627472076,
%T A294039 966858672404690,330665665962404000,138879579704209680022,
%U A294039 70273067330330098091156,42163840398198058854693626,29599015959535037315994925480,24034400959142450300587879489790
%N A294039 a(n) = e*Gamma(2*n,1).
%H A294039 Robert Israel, <a href="/A294039/b294039.txt">Table of n, a(n) for n = 1..225</a>
%F A294039 From _Robert Israel_, Nov 14 2017: (Start)
%F A294039 a(n) = (2*n-1)!*Sum_{k=0..2*n-1} 1/k!.
%F A294039 a(n+1) = 2*n*(2*n+1)*a(n) + 2*n+2. (End)
%p A294039 a := n -> exp(1)*GAMMA(2*n,1):
%p A294039 seq(simplify(a(n)), n=1..15);
%p A294039 # Alternate:
%p A294039 f:= gfun:-rectoproc({a(n+1) = 2*n*(2*n+1)*a(n) + 2*n+2, a(1) = 2},a(n),remember):
%p A294039 map(f, [$1..20]); # _Robert Israel_, Nov 14 2017
%t A294039 Array[E Gamma[2 #, 1] &, 15] (* _Michael De Vlieger_, Nov 14 2017 *)
%Y A294039 Bisection of A000522. Cf. A294040.
%K A294039 nonn
%O A294039 1,1
%A A294039 _Peter Luschny_, Nov 14 2017