A026119 Bisection of A000016 (also of A000013).

1, 2, 4, 10, 30, 94, 316, 1096, 3856, 13798, 49940, 182362, 671092, 2485534, 9256396, 34636834, 130150588, 490853416, 1857283156, 7048151672, 26817356776, 102280151422, 390937468408, 1497207322930, 5744387279818, 22076468764192

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

Cf. A000013, A000016, A000116.

Bisection of A053634 and A053656.

Sequence in context: A361758 A148116 A149833 * A149834 A273958 A362637

Adjacent sequences: A026116 A026117 A026118 * A026120 A026121 A026122

Keyword

nonn

Author

N. J. A. Sloane, Apr 12 2000

Status

approved