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 A279881 #10 Dec 22 2016 23:36:52
%S A279881 1,8,1056,5529600,2040024268800,82038030902231040000,
%T A279881 512596445591262883479552000000,
%U A279881 671373457257855830831011844849664000000000,238977230623673235057124486022413812190150656000000000000
%N A279881 a(n) = A168467(n) * Sum_{k=0..n}(2^k*(k!)^2 / (2*k+1)!).
%H A279881 Daniel Suteu, <a href="/A279881/b279881.txt">Table of n, a(n) for n = 0..19</a>
%F A279881 a(n) ~ Pi/2 * A168467(n).
%F A279881 a(0) = 1, a(n) = a(n-1) * (2*n + 1)! + 2^n * (n!)^2 * A168467(n-1).
%t A279881 Table[Product[((2 k + 2) (2 k + 3))^(n - k), {k, 0, n}] Sum[(2^j*(j!)^2/(2 j + 1)!), {j, 0, n}], {n, 0, 8}] (* _Michael De Vlieger_, Dec 22 2016 *)
%o A279881 (PARI) a(n) = prod(k=1, n, (2*k+1)!) * sum(k=0, n, 2^k * (k!)^2 / (2*k+1)!)
%Y A279881 Cf. A168467.
%K A279881 nonn,easy
%O A279881 0,2
%A A279881 _Daniel Suteu_, Dec 21 2016