OFFSET
0,1
LINKS
Max Alekseyev, Table of n, a(n) for n = 0..561
FORMULA
a(n) = A046798(2*n). - Max Alekseyev, Jan 08 2024
EXAMPLE
a(3)=4 because 4^3+1 has divisors {1, 5, 13, 65}.
MAPLE
a:=n->numtheory[tau](4^n+1):
seq(a(n), n=0..100);
MATHEMATICA
DivisorSigma[0, 4^Range[0, 100]+1] (* Paolo Xausa, Oct 14 2023 *)
PROG
(PARI) a(n) = numdiv(4^n+1);
(Python)
from sympy import divisor_count
def A366606(n): return divisor_count((1<<(n<<1))+1) # Chai Wah Wu, Oct 14 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
Sean A. Irvine, Oct 14 2023
STATUS
approved