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%I #13 Jun 21 2021 16:27:42
%S 1,8,192,16384,5242880,6442450944,30786325577728,576460752303423488,
%T 42501298345826806923264,12379400392853802748991242240,
%U 14278816360970775978458864905355264,65334214448820184984967924626899496599552,1187470080331358621040493926581979953470445191168
%N a(n) = (n+1)*2^(n*(n+1)).
%C Hankel transform of A069723.
%C With offset 1, a(n) is the number of vertices with in-degree = 0 over all labeled digraphs (with self loops allowed) on n vertices. Equivalently, the number of elements in all labeled relations on an n-set that have no preimage. - _Geoffrey Critzer_, Aug 16 2016
%F a(n) = A095340(n)*A006125(n+1).
%t Table[n 2^(n - 1) 2^(n - 1)^2, {n, 1, 10}]
%t Table[(n+1)2^(n(n+1)),{n,0,20}] (* _Harvey P. Dale_, Jun 21 2021 *)
%Y Cf. A006125, A069723, A095340.
%K easy,nonn
%O 0,2
%A _Paul Barry_, Mar 01 2007
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