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 A100444 #13 Jul 27 2022 08:49:33
%S A100444 1,3,53,2119,148329,16019531,2467007773,513137616783,138547156531409,
%T A100444 47106033220679059,19690321886243846661,9923922230666898717143,
%U A100444 5934505493938805432851513,4154153845757163802996059099
%N A100444 Bisection of A000255.
%F A100444 a(n) = (2*n + 1)!*hypergeom([-2*n], [-2*n - 1], -1). - _Peter Luschny_, Nov 02 2018
%F A100444 D-finite with recurrence a(n) +(-4*n^2-2*n+1)*a(n-1) +2*n*(2*n-3)*a(n-2)=0. - _R. J. Mathar_, Jul 27 2022
%p A100444 a := n -> (2*n+1)!*hypergeom([-2*n],[-2*n-1],-1):
%p A100444 seq(simplify(a(n)), n=0..13); # _Peter Luschny_, Nov 02 2018
%t A100444 a[n_] := (2n)! SeriesCoefficient[E^-x / (1-x)^2, {x, 0, 2n}];
%t A100444 Table[a[n], {n, 0, 13}] (* _Jean-François Alcover_, Jun 11 2019 *)
%Y A100444 Cf. A000255.
%K A100444 nonn,easy
%O A100444 0,2
%A A100444 _N. J. A. Sloane_, Nov 21 2004
%E A100444 More terms from _Hugo Pfoertner_, Nov 26 2004