OFFSET
2,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 2..1206
FORMULA
MATHEMATICA
Table[EulerPhi[(2^n - 1)]/2, {n, 2, 40}]
PROG
(PARI) a(n) = eulerphi(2^n - 1)/2; \\ Amiram Eldar, Jun 09 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Aug 14 2000
STATUS
approved