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A127888 If X_1,...,X_n is a partition of a 6n-set X into 6-blocks then a(n) is equal to the number of permutations f of X such that f(X_i)<>X_i, (i=1,...n).

%I A127888 #3 Mar 31 2012 13:21:47
%S A127888 0,478483200,6401339808768000,620429964386047303680000,
%T A127888 265250626231132937174895820800000,
%U A127888 371992180902371387782970387300352000000000
%N A127888 If X_1,...,X_n is a partition of a 6n-set X into 6-blocks then a(n) is equal to the number of permutations f of X such that f(X_i)<>X_i, (i=1,...n).
%H A127888 Milan Janjic, <a href="http://www.pmfbl.org/janjic/">Enumerative Formulas for Some Functions on Finite Sets</a>
%F A127888 a(n)=sum((-720)^i*binomial(n,i)*(6*n-6*i)!,i=0..n).
%e A127888 a(5)=265250626231132937174895820800000
%p A127888 a:=n->sum((-720)^i*binomial(n,i)*(6*n-6*i)!,i=0..n).
%K A127888 nonn
%O A127888 1,2
%A A127888 _Milan Janjic_, Apr 09 2007