A390727 - OEIS

%I #13 Nov 19 2025 07:52:18

%S 1,1,28,2700,571536,214326000,125799886080,106657796044800,

%T 123488975062252800,187327646047474732800,360672808042354114944000,

%U 859499837892824747191372800,2483997739853162371289966592000,8560829696851107798143961139200000,34689216250915892757838200777523200000

%N a(n) = Stirling2(2*n, n)*(2*n)!/(n+1)!.

%H Vincenzo Librandi, <a href="/A390727/b390727.txt">Table of n, a(n) for n = 0..195</a>

%F a(n) = A048993(2*n, n)*A001761(n).

%F a(n) = A007820(n)*A001761(n).

%F a(n) = n!*A390277(n).

%p A390727 := n -> Stirling2(2*n, n)*(2*n)!/(n+1)!:

%p seq(A390727(n), n = 0..14);

%t Table[StirlingS2[2 n,n]*Factorial[2 n]/Factorial[n+1],{n,0,15}] (* _Vincenzo Librandi_, Nov 19 2025 *)

%o (Magma) [StirlingSecond(2*n, n)*Factorial(2*n)/Factorial(n+1): n in [0..20]]; // _Vincenzo Librandi_, Nov 19 2025

%Y Cf. A390277, A390276, A390276, A048993, A007820, A001761.

%K nonn

%O 0,3

%A _Peter Luschny_, Nov 16 2025