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a(n) = (n-1)! * Product_{i=1..n-1} ((2*n)!-2*i-1).
0

%I #9 Jul 10 2020 00:00:26

%S 1,21,1025310,393143628567690,4161601591128480023923529880,

%T 3025979870886810157320547152897281546399520600,

%U 316069513961213168272637175554794298273860325049869267706740636689200

%N a(n) = (n-1)! * Product_{i=1..n-1} ((2*n)!-2*i-1).

%D Barry Simon, Representations of Finite and Compact Groups, AMS, p. 233.

%t Table[(n - 1)!*Product[(2 n)! - 2 i - 1, {i, n - 1}], {n, 7}] (* _Wesley Ivan Hurt_, May 07 2014 *)

%K nonn,easy

%O 1,2

%A _N. J. A. Sloane_, Dec 11 1999