A336101 Numbers divisible by exactly one odd prime.

3, 5, 6, 7, 9, 10, 11, 12, 13, 14, 17, 18, 19, 20, 22, 23, 24, 25, 26, 27, 28, 29, 31, 34, 36, 37, 38, 40, 41, 43, 44, 46, 47, 48, 49, 50, 52, 53, 54, 56, 58, 59, 61, 62, 67, 68, 71, 72, 73, 74, 76, 79, 80, 81, 82, 83, 86, 88, 89, 92, 94, 96, 97, 98, 100, 101, 103, 104

Offset: 1

Author

Peter Munn, Jul 08 2020

Keywords

• nonn
• easy

Comments

Numbers k for which A001221(A000265(k)) = 1. - Antti Karttunen, Jul 08 2020

Numbers whose odd part is a prime power (A246655). - Amiram Eldar, Jul 08 2020

Numbers of the form 2^r * p^q with p an odd prime (A065091), r >= 0, q >= 1. - Bernard Schott, Dec 14 2020

Links

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

Crossrefs

Cf. A000265, A001221, A246655, A340373 (characteristic function).

Positions of ones in A005087.

Subsequence of A267895.

Subsequences: A007283 (3*2^n), A020714 (5*2^n), A005009 (7*2^n), A005015 (11*2^n), A005029 (13*2^n), A038550 (p*2^n, p odd prime), A065091 (odd primes), A061345 \ {1} (odd prime powers).

Programs

Mathematica

Select[Range[104], PrimePowerQ[#/2^IntegerExponent[#, 2]] &] (* Amiram Eldar, Jul 08 2020 *)

PARI

isA336101(n) = (1==omega(n>>valuation(n,2))); \\ Antti Karttunen, Jul 08 2020