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 A151817 #31 Aug 02 2023 13:52:00
%S A151817 2,4,24,240,3360,60480,1330560,34594560,1037836800,35286451200,
%T A151817 1340885145600,56317176115200,2590590101299200,129529505064960000,
%U A151817 6994593273507840000,405686409863454720000,25152557411534192640000,1660068789161256714240000,116204815241287969996800000
%N A151817 a(n) = 2*(2*n)!/n!.
%C A151817 (n+1)*a(n) is the number of random walk labelings of the comb graph of length n+1. - _Sela Fried_, Aug 02 2023
%H A151817 G. C. Greubel, <a href="/A151817/b151817.txt">Table of n, a(n) for n = 0..364</a>
%H A151817 Sela Fried and Toufik Mansour, <a href="https://arxiv.org/abs/2308.00315">Random walk labelings of perfect trees and other graphs</a>, arXiv:2308.00315 [math.CO], 2023.
%F A151817 From _Alexander R. Povolotsky_, Jul 06 2009: (Start)
%F A151817 a(n) = 2^(2*n + 1)* Pochhammer(1/2, n).
%F A151817 a(n) = 2^(2*n + 1)*Gamma(n + 1/2) / Gamma(1/2) = 2^(2*n+1)*Gamma(n+1/2)/sqrt(Pi).
%F A151817 a(n) = 2*(2*n - 1)*a(n-1). (End) [Updated by _Peter Luschny_, Aug 02 2023]
%F A151817 E.g.f.: 2/(1-4*x)^(1/2).- _Sergei N. Gladkovskii_, Dec 05 2011
%F A151817 G.f.: G(0), where G(k)= 1 + 1/(1 - x*(4*k+2)/(x*(4*k+2) + 1/G(k+1))); (continued fraction). - _Sergei N. Gladkovskii_, Jun 04 2013
%F A151817 a(n) = A052718(n+1), n>0.
%F A151817 a(n) = 2*A001813(n). - _R. J. Mathar_, Mar 12 2017
%t A151817 Table[2*(2*n)!/n!, {n, 0, 50}] (* _G. C. Greubel_, Feb 21 2017 *)
%o A151817 (PARI) a(n)=2*(2*n)!/n! \\ _Charles R Greathouse IV_, Dec 05 2011
%Y A151817 Cf. A052718, A001813, row sums of A155951.
%K A151817 nonn,easy
%O A151817 0,1
%A A151817 _Roger L. Bagula_, Jan 31 2009
%E A151817 Typo in definition corrected by _N. J. A. Sloane_, Jul 12 2009
%E A151817 New name from _Sergei N. Gladkovskii_, Dec 05 2011