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 A014298 #21 Mar 01 2025 17:44:10
%S A014298 1,2,24,576,21120,1048320,65802240,5000970240,446557224960,
%T A014298 45830873088000,5316381278208000,687893507997696000,
%U A014298 98231192942070988800,15345895252950201139200,2603510504983275503616000,476694375041453927694336000,93692112621783944697741312000
%N A014298 a(n) = 2^n * (3n)! / (2n+1)!.
%H A014298 G. C. Greubel, <a href="/A014298/b014298.txt">Table of n, a(n) for n = 0..250</a>
%F A014298 From _G. C. Greubel_, Jun 12 2019: (Start)
%F A014298 G.f.: Hypergeometric3F1(1/3, 2/3, 1; 3/2; 27*x/2).
%F A014298 E.g.f.: sqrt(2/(3*x)) * sin( arcsin(sqrt(27*x/2))/3 ).
%F A014298 E.g.f.: hypergeometric2F1(1/3, 2/3; 3/2; 27*x/2) (End)
%t A014298 Table[2^n (3n)!/(2n+1)!,{n,0,20}] (* _Harvey P. Dale_, Mar 19 2016 *)
%o A014298 (PARI) a(n) = 2^n * (3*n)! / (2*n+1)! \\ _Michel Marcus_, Jun 24 2013
%o A014298 (Magma) [2^n*Factorial(3*n)/Factorial(2*n+1): n in [0..20]]; // _G. C. Greubel_, Jun 12 2019
%o A014298 (Sage) [2^n*factorial(3*n)/factorial(2*n+1) for n in (0..20)] # _G. C. Greubel_, Jun 12 2019
%o A014298 (GAP) List([0..20], n-> 2^n*Factorial(3*n)/Factorial(2*n+1) ); # _G. C. Greubel_, Jun 12 2019
%K A014298 nonn,easy
%O A014298 0,2
%A A014298 _Igor Pak_