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%I #7 Feb 06 2017 20:14:00
%S 0,2,6,36,180,1320,9240,84000,756000,8285760,91143360,1173553920,
%T 15256200960,226040855040,3390612825600,56865153945600,
%U 966707617075200,18112111963545600,344130127307366400,7125892746964992000
%N a(n) = n! * Sum_{k=1..floor(n/2)} 1/k.
%F a(1) = 0, a(n) = a(n-1)*n + (1 + (-1)^n)*(n-1)!. - _Daniel Suteu_, Feb 06 2017
%t Table[ n! HarmonicNumber[ Floor[ n/2]], {n, 20}] (* _Robert G. Wilson v_, Dec 11 2004 *)
%Y Cf. A101610, A101611, A101612, A101613, A000254, A046673, A052517.
%K nonn,easy
%O 1,2
%A _Ralf Stephan_, Dec 10 2004
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