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A300843
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Number of 4-cycles in the n-transposition graph.
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2
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0, 0, 9, 162, 2250, 29700, 396900, 5503680, 80015040, 1224720000, 19758816000, 335899872000, 6010631827200, 113048449113600, 2231219390400000, 46134751703040000, 997703235809280000, 22529953070456832000, 530433460332711936000, 13000820106193920000000
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OFFSET
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1,3
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LINKS
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FORMULA
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a(n) = 3*n!*(2*binomial(n,3) + binomial(n,4))/4. - Andrew Howroyd, Mar 13 2018
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MATHEMATICA
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Table[3 n! (2 Binomial[n, 3] + Binomial[n, 4])/4, {n, 25}] (* Vincenzo Librandi, Mar 14 2018 *)
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PROG
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(PARI) a(n)={3*n!*(2*binomial(n, 3)+binomial(n, 4))/4} \\ Andrew Howroyd, Mar 13 2018
(Magma) [3*Factorial(n)*(2*Binomial(n, 3)+Binomial(n, 4))/4: n in [1..20]]; // Vincenzo Librandi, Mar 14 2018
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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