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A087905
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a(n) = n! * Sum_{d|n} (d/n)^d.
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3
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1, 3, 8, 36, 144, 1010, 5760, 50400, 416640, 4250232, 43545600, 553106400, 6706022400, 95865541200, 1410695430144, 22720842144000, 376610217984000, 6888030445296000, 128047474114560000, 2587520533615041024
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OFFSET
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1,2
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LINKS
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FORMULA
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E.g.f.: Sum_{k>0} x^k/(k-x^k).
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MATHEMATICA
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a[n_]:= n!*DivisorSum[n, (#/n)^# &]; Array[a, 50] (* G. C. Greubel, May 16 2018 *)
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PROG
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(PARI) {a(n)= n!*sumdiv(n, d, (d/n)^d)};
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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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