OFFSET
0,1
LINKS
Max Alekseyev, Table of n, a(n) for n = 0..345
FORMULA
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);
CROSSREFS
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 15 2023
STATUS
approved