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

Author

Waldemar Puszkarz, Mar 06 2016

Keywords

• nonn

Comments

Contains A046642.

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

Examples

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

Links

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

Crossrefs

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

Programs

Mathematica

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

PARI

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