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A366637
Number of divisors of 7^n+1.
9
2, 4, 6, 8, 4, 16, 24, 16, 8, 16, 32, 16, 32, 16, 12, 64, 8, 8, 48, 16, 16, 128, 48, 8, 16, 32, 24, 32, 64, 8, 512, 32, 16, 128, 48, 1024, 256, 16, 12, 256, 64, 64, 96, 512, 32, 2048, 96, 8, 64, 2048, 640, 128, 32, 64, 384, 3072, 256, 256, 96, 64, 512, 8, 48
OFFSET
0,1
LINKS
FORMULA
a(n) = sigma0(7^n+1) = A000005(A034491(n)).
EXAMPLE
a(4)=4 because 7^4+1 has divisors {1, 2, 1201, 2402}.
MAPLE
a:=n->numtheory[tau](7^n+1):
seq(a(n), n=0..100);
MATHEMATICA
DivisorSigma[0, 7^Range[0, 62] + 1] (* Paul F. Marrero Romero, Oct 16 2023 *)
PROG
(PARI) a(n) = numdiv(7^n+1);
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 15 2023
STATUS
approved