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a(n) = ((2n)!)^2.
7

%I #11 Nov 16 2020 03:38:47

%S 1,4,576,518400,1625702400,13168189440000,229442532802560000,

%T 7600054456551997440000,437763136697395052544000000,

%U 40990389067797283140009984000000,5919012181389927685417441689600000000

%N a(n) = ((2n)!)^2.

%F From _Amiram Eldar_, Nov 16 2020: (Start)

%F Sum_{n>=0} 1/a(n) = A334379.

%F Sum_{n>=0} (-1)^n/a(n) = A334632. (End)

%t Table[((2n)!)^(2), {n, 0, 10}]

%t ((2*Range[0,20])!)^2 (* _Harvey P. Dale_, Jul 14 2011 *)

%o (PARI) a(n) = ((2*n)!)^2; \\ _Michel Marcus_, Nov 16 2020

%Y Cf. A000142, A001044, A000442, A036740, A010050, A134366, A134367, A134368, A134369, A134371, A134374, A134375, A334379, A334632.

%K nonn

%O 0,2

%A _Artur Jasinski_, Oct 22 2007