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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). 1

%I #3 Mar 31 2012 13:21:47

%S 0,478483200,6401339808768000,620429964386047303680000,

%T 265250626231132937174895820800000,

%U 371992180902371387782970387300352000000000

%N 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 Milan Janjic, <a href="http://www.pmfbl.org/janjic/">Enumerative Formulas for Some Functions on Finite Sets</a>

%F a(n)=sum((-720)^i*binomial(n,i)*(6*n-6*i)!,i=0..n).

%e a(5)=265250626231132937174895820800000

%p a:=n->sum((-720)^i*binomial(n,i)*(6*n-6*i)!,i=0..n).

%K nonn

%O 1,2

%A _Milan Janjic_, Apr 09 2007

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Last modified April 25 08:27 EDT 2024. Contains 371964 sequences. (Running on oeis4.)