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 A116220 If X_1,...,X_n is a partition of a 4n-set X into 4-blocks then a(n) is equal to the number of permutations f of X such that f(X_i) <> X_i, (i=1,...,n). 3

%I #12 Sep 08 2022 08:45:24

%S 0,39744,476126208,20876944084992,2430394026897309696,

%T 620098244484731975761920,304784138698487640049544331264,

%U 263072308376236973471661993731555328,371936496850567880606221498503260339699712,815826011669313721421241471652159968573722198016

%N If X_1,...,X_n is a partition of a 4n-set X into 4-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 G. C. Greubel, <a href="/A116220/b116220.txt">Table of n, a(n) for n = 1..110</a>

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

%F a(n) = Sum_{j=0..n} (-24)^j*binomial(n,j)*(4*n-4*j)!.

%p a:=n->sum((-24)^i*binomial(n,i)*(4*n-4*i)!,i=0..n).

%t Table[Sum[(-24)^j*Binomial[n, j]*(4*n-4*j)!, {j,0,n}], {n, 1, 20}] (* _G. C. Greubel_, May 11 2019 *)

%o (PARI) {a(n) = sum(j=0,n, (-24)^j*binomial(n,j)*(4*(n-j))!)}; \\ _G. C. Greubel_, May 11 2019

%o (Magma) [(&+[(-24)^j*Binomial(n, j)*Factorial(4*n-4*j): j in [0..n]]): n in [1..20]]; // _G. C. Greubel_, May 11 2019

%o (Sage) [sum((-24)^j*binomial(n,j)*factorial(4*n-4*j) for j in (0..n)) for n in (1..20)] # _G. C. Greubel_, May 11 2019

%o (GAP) List([1..20], n-> Sum([0..n], j-> (-24)^j*Binomial(n,j)* Factorial(4*n-4*j))) # _G. C. Greubel_, May 11 2019

%Y Cf. A116218, A116219, A116221.

%K nonn

%O 1,2

%A _Milan Janjic_, Apr 09 2007

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Last modified June 8 14:02 EDT 2023. Contains 363165 sequences. (Running on oeis4.)