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A305465
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a(n) = Sum_{k=0..floor(n/2)} ((n-k)!/k!)*binomial(n-k,k)*n^(n-2*k).
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3
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1, 1, 9, 174, 6433, 387045, 34372513, 4223468872, 685727920641, 142133068151865, 36615156774045001, 11474421446955693006, 4298048476279871328289, 1896322606147540294800349, 973319784969445114237699713, 575000041101937659730069884960
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OFFSET
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0,3
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LINKS
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FORMULA
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MATHEMATICA
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Join[{1}, Table[Sum[(n-k)!/k! Binomial[n-k, k]n^(n-2k), {k, 0, Floor[n/2]}], {n, 20}]] (* Harvey P. Dale, Sep 22 2019 *)
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PROG
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(PARI) {a(n) = sum(k=0, n/2, ((n-k)!/k!)*binomial(n-k, k)*n^(n-2*k))}
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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