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 A264153 #12 Jan 08 2025 13:10:43 %S A264153 1,2,144,64800,101606400,411505920000,3585039575040000, %T A264153 59375425441812480000,1710012252724199424000000, %U A264153 80059353648041568632832000000,5780285333388601255290470400000000,616883611349898303167109582028800000000,93983451956379706284115479041251737600000000 %N A264153 a(n) = ((2*n)!)^2 / 2^n. %F A264153 a(n) = A134372(n)/A000079(n). %F A264153 a(n)*A264152(n) = A134372(n)*A006882(2*n-1)/A006882(n). %F A264153 a(n)/A264152(n) is an integer: 1, 1, 24, 1620,.... %p A264153 a := n -> (2*n)!^2/2^n; seq(a(n), n=0..10); %o A264153 (Sage) %o A264153 a = lambda n: factorial(2*n)^2 >> n %o A264153 [a(n) for n in range(11)] %Y A264153 Cf. A000079, A000680, A134372, A264152. %K A264153 nonn %O A264153 0,2 %A A264153 _Peter Luschny_, Nov 06 2015