OFFSET
1,2
COMMENTS
a(0) cannot be defined because 0's divisors are an infinite set (every number is a divisor of 0.)
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..1206 (terms 1..500 from T. D. Noe)
EXAMPLE
a(120) = 73728 since 2^120-1 has that many divisors.
MAPLE
a:= n-> numtheory[tau](2^n-1):
seq(a(n), n=1..80); # Alois P. Heinz, Aug 23 2021
MATHEMATICA
Table[DivisorSigma[0, 2^n - 1], {n, 120}] (* Michael De Vlieger, Mar 26 2015 *)
PROG
(PARI) a(n) = numdiv(2^n-1); \\ Michel Marcus, Dec 15 2013
(Magma) [DivisorSigma(0, 2^n - 1): n in [1..100]]; // Vincenzo Librandi, Mar 27 2015
(Python)
from sympy import divisor_count
def A046801(n): return divisor_count((1<<n)-1) # Chai Wah Wu, Mar 13 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Typo in example fixed by Reinhard Zumkeller, May 15 2010
a(0) removed by J. Lowell, Mar 26 2015
STATUS
approved