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A366665
Number of divisors of 9^n+1.
9
2, 4, 4, 8, 8, 12, 8, 16, 4, 16, 8, 16, 64, 16, 16, 48, 4, 16, 16, 16, 32, 128, 32, 16, 16, 128, 16, 32, 64, 16, 128, 32, 4, 64, 32, 384, 256, 32, 64, 128, 32, 32, 1024, 128, 64, 384, 16, 16, 64, 512, 64, 256, 128, 64, 512, 192, 512, 512, 32, 8, 2048, 64, 16
OFFSET
0,1
LINKS
FORMULA
a(n) = sigma0(9^n+1) = A000005(A062396(n)).
a(n) = A366577(2*n). - Max Alekseyev, Jan 08 2024
EXAMPLE
a(2)=4 because 9^2+1 has divisors {1, 2, 41, 82}.
MAPLE
a:=n->numtheory[tau](9^n+1):
seq(a(n), n=0..100);
MATHEMATICA
DivisorSigma[0, 9^Range[0, 62] + 1] (* Paul F. Marrero Romero, Nov 13 2023 *)
PROG
(PARI) a(n) = numdiv(9^n+1);
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 15 2023
STATUS
approved