OFFSET
1,1
LINKS
Max Alekseyev, Table of n, a(n) for n = 1..500
FORMULA
a(n) = A046801(3*n). - Max Alekseyev, Jan 09 2024
EXAMPLE
a(5)=8 because 8^5-1 has divisors {1, 7, 31, 151, 217, 1057, 4681, 32767}.
MAPLE
a:=n->numtheory[tau](8^n-1):
seq(a(n), n=1..100);
MATHEMATICA
DivisorSigma[0, 8^Range[100]-1]
PROG
(PARI) a(n) = numdiv(8^n-1);
CROSSREFS
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 15 2023
STATUS
approved