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A366633
Number of divisors of 7^n-1.
11
4, 10, 12, 36, 8, 60, 16, 84, 64, 80, 16, 864, 8, 160, 96, 384, 16, 640, 16, 1536, 96, 160, 32, 16128, 32, 80, 1280, 1152, 32, 3840, 32, 1728, 384, 80, 128, 18432, 32, 160, 192, 14336, 32, 7680, 16, 4608, 2048, 160, 16, 147456, 256, 640, 768, 1152, 32, 25600
OFFSET
1,1
LINKS
FORMULA
a(n) = sigma0(7^n-1) = A000005(A024075(n)).
EXAMPLE
a(5)=8 because 7^5-1 has divisors {1, 2, 3, 6, 2801, 5602, 8403, 168061}.
MAPLE
a:=n->numtheory[tau](7^n-1):
seq(a(n), n=1..100);
MATHEMATICA
DivisorSigma[0, 7^Range[100]-1]
PROG
(PARI) a(n) = numdiv(7^n-1);
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 14 2023
STATUS
approved