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a(n) = (n*(n+1)/2+1)!/n!.
1

%I #7 Jun 09 2023 23:18:53

%S 1,2,12,840,1663200,174356582400,1561112121913344000,

%T 1754317855900734514790400000,341362923889542287855059017400320000000,

%U 15163751542692044063740921044974247390216192000000000,195932150519417838363658963697014150610807423633478962380800000000000

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

%t Table[(n (n+1)/2+1)!/n!,{n,0,20}] (* _Harvey P. Dale_, Aug 04 2022 *)

%Y Cf. A000124, A107868, A129893.

%K nonn

%O 0,2

%A _N. J. A. Sloane_, Jun 06 2007