OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..400
FORMULA
MATHEMATICA
Table[DivisorSigma[1, EulerPhi[2^n - 1]], {n, 1, 30}]
PROG
(PARI) a(n) = sigma(eulerphi(2^n-1)); \\ Michel Marcus, Aug 30 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Jul 19 2004
EXTENSIONS
More terms from Michel Marcus, Aug 30 2019
STATUS
approved