OFFSET
0,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..1666
FORMULA
a(n) = (Sum_{d | 2n+1} phi(d)*2^((2n+1)/d)) / (4n+2).
PROG
(PARI) a(n) = sumdiv(2*n+1, d, eulerphi(d)*2^((2*n+1)/d)) / (4*n+2); \\ Michel Marcus, Sep 11 2013
(Python)
from sympy import totient, divisors
def A026119(n):
m = (n<<1)+1
return sum(totient(d)<<m//d-1 for d in divisors(m, generator=True))//m # Chai Wah Wu, Feb 21 2023
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Apr 12 2000
STATUS
approved