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A366757
a(n) is the sum of the divisors of n!-1.
3
1, 6, 24, 144, 720, 5040, 42096, 399000, 3753960, 47500992, 479001600, 6230615736, 87178291200, 1457696910960, 20929670124480, 379536693283440, 6510917252872320, 121831439598033840, 2432921507427445440, 53921727651043042560, 1134312679767378217920
OFFSET
2,2
FORMULA
a(n) = sigma(n!-1) = A000203(A033312(n)).
EXAMPLE
a(5) = 144 because the divisors of 5!-1 are {1, 7, 17, 119}.
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 *)
PROG
(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
CROSSREFS
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 20 2023
STATUS
approved