A006548 - OEIS

%I #7 May 22 2013 16:15:43

%S 0,24,480,40320,2903040,479001600,74724249600,20922789888000,

%T 5690998849536000,2432902008176640000,1021818843434188800000,

%U 620448401733239439360000,372269041039943663616000000

%N (2*n)!-Sum ((-1)^(i+1)*binomial(n,i)*2^i*(2*n-1)!,i=1..n).

%F 4*floor(n/2) * (2n-1)!. - _Ralf Stephan_, Mar 08 2004

%K nonn

%O 1,2

%A _N. J. A. Sloane_.