A366757 a(n) is the sum of the divisors of n!-1.

1, 6, 24, 144, 720, 5040, 42096, 399000, 3753960, 47500992, 479001600, 6230615736, 87178291200, 1457696910960, 20929670124480, 379536693283440, 6510917252872320, 121831439598033840, 2432921507427445440, 53921727651043042560, 1134312679767378217920

Offset: 2

Author

Sean A. Irvine, Oct 20 2023

Keywords

• nonn

Examples

			a(5) = 144 because the divisors of 5!-1 are {1, 7, 17, 119}.
		

Crossrefs

Cf. A033312, A000203, A064145, A062569, A366758.

Programs

Maple

a:=n->numtheory[sigma](n!-1):
seq(a(n), n=2..30);

Mathematica

DivisorSigma[1,Range[2,25]!-1] (* Paolo Xausa, Oct 21 2023 *)

Python

from math import factorial
from sympy import divisor_sigma
def A366757(n): return divisor_sigma(factorial(n)-1) # Chai Wah Wu, Oct 20 2023

Formula

a(n) = sigma(n!-1) = A000203(A033312(n)).