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%I #27 Nov 29 2020 02:09:35
%S 2,64,7776,2097152,1000000000,743008370688,793714773254144,
%T 1152921504606846976,2185911559738696531968,5242880000000000000000000,
%U 15519448971100888972574851072,55572324035428505185378394701824,236773830007967588876795164938469376
%N a(n) = (2n)^(2n-1).
%C a(0) is 0^(-1) = 1/0, which is undefined.
%F a(n) = A005843(n)^A005408(n-1). - _Michel Marcus_, Apr 14 2018
%F Sum_{n>=1} 1/a(n) = A338167. - _Amiram Eldar_, Nov 29 2020
%t Table[(2*n)^(2*n - 1), {n, 20}] (* _T. D. Noe_, Feb 26 2013 *)
%Y Cf. A005408, A005843, A222621, A338167.
%K nonn
%O 1,1
%A _N. J. A. Sloane_, Jul 05 2003