A325435 Numbers m such that m! / sigma(m) is an integer.

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

Offset

1,2

Comments

Complement of A325436.

Corresponding integers are 1, 20, 60, 630, 2688, 201600, 3326400, 17107200, ...

Equals A163162 without number 3.

Links

Table of n, a(n) for n=1..66.

Example

6 is in the sequence because 6! / sigma(6) = 720 / 12 = 60 (integer).

Mathematica

Select[Range[80], IntegerQ[#!/DivisorSigma[1, #]]&] (* Harvey P. Dale, Jul 20 2022 *)

Prog

(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

Crossrefs

Cf. A000142, A000203, A053182, A163162, A325436.

Sequence in context: A051052 A119368 A088721 * A288857 A201472 A005049

Adjacent sequences: A325432 A325433 A325434 * A325436 A325437 A325438

Keyword

nonn

Author

Jaroslav Krizek, Apr 26 2019

Status

approved