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%I #10 Mar 07 2020 23:33:40
%S 0,1,10,90,1392,18675,409104,7411348,209085952,4788571365,
%T 164757984000,4571341663086,185247857018880,6045063784869655,
%U 281596888593405952,10574853536725785000,556202715633735696384,23639922913364842592457
%N a(n) = (1/2)*(n+1)!*Sum_{k=0..floor(n/2)} n^(2k+1)/(2k+1)!.
%H Andrew Howroyd, <a href="/A046706/b046706.txt">Table of n, a(n) for n = 0..200</a>
%t Table[(n+1)!/2 Sum[n^(2k+1)/(2k+1)!,{k,0,Floor[n/2]}],{n,0,20}] (* _Harvey P. Dale_, Mar 05 2013 *)
%o (PARI) a(n) = {(n+1)!*sum(k=0, n\2, n^(2*k+1)/(2*k+1)!)/2} \\ _Andrew Howroyd_, Mar 07 2020
%K nonn
%O 0,3
%A _N. J. A. Sloane_
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