A269870 Numbers coprime to the number of their odd divisors.

1, 2, 3, 4, 5, 7, 8, 11, 13, 15, 16, 17, 19, 21, 23, 25, 27, 29, 31, 32, 33, 35, 37, 39, 41, 43, 47, 49, 50, 51, 53, 55, 57, 59, 61, 64, 65, 67, 69, 71, 73, 77, 79, 81, 83, 85, 87, 89, 91, 93, 95, 97, 98, 100, 101, 103, 105, 107, 109, 111, 113, 115, 119, 121, 123, 125, 127, 128, 129, 131, 133, 135, 137, 139, 141, 143, 145, 149, 151, 155

Offset

1,2

Comments

Contains A046642.

Conjecture: the asymptotic density of this sequence is the same as that of A046642.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

For n=2, a(2)=2 is a term as the number of odd divisors of 2 is 1, which is coprime to 2.

Mathematica

Select[Range@200, CoprimeQ[#, Length@Select[Divisors[#], OddQ]]&]

Prog

(PARI) for(n=1, 200, gcd(n, sumdivmult(n, d, d%2))==1&&print1(n, ", "))

Crossrefs

Cf. A001227 (number of odd divisors), A046642 (numbers coprime to the number of their divisors), A269818 (counterpart for the number of even divisors).

Sequence in context: A177202 A053868 A241912 * A307824 A081730 A162408

Adjacent sequences: A269867 A269868 A269869 * A269871 A269872 A269873

Keyword

nonn

Author

Waldemar Puszkarz, Mar 06 2016

Status

approved