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A325435
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Numbers m such that m! / sigma(m) is an integer.
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1
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1, 5, 6, 7, 8, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 24, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 65, 66, 67, 68, 69, 70, 71, 72, 73
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OFFSET
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1,2
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COMMENTS
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Corresponding integers are 1, 20, 60, 630, 2688, 201600, 3326400, 17107200, ...
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LINKS
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EXAMPLE
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6 is in the sequence because 6! / sigma(6) = 720 / 12 = 60 (integer).
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MATHEMATICA
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Select[Range[80], IntegerQ[#!/DivisorSigma[1, #]]&] (* Harvey P. Dale, Jul 20 2022 *)
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PROG
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(Magma) [n: n in [1..1000] | IsIntegral(Factorial(n)/&+[d: d in Divisors(n)])]
(PARI) isok(n) = ((n! % sigma(n)) == 0); \\ Michel Marcus, Apr 26 2019
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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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