A247180 Numbers with nonrepeating smallest prime factor.

2, 3, 5, 6, 7, 10, 11, 13, 14, 15, 17, 18, 19, 21, 22, 23, 26, 29, 30, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 46, 47, 50, 51, 53, 54, 55, 57, 58, 59, 61, 62, 65, 66, 67, 69, 70, 71, 73, 74, 75, 77, 78, 79, 82, 83, 85, 86, 87, 89, 90, 91, 93, 94, 95, 97, 98

Offset: 1

Author

Reinhard Zumkeller, Nov 23 2014

Keywords

• nonn

Comments

Complement of the union of {1} and A283050. The asymptotic density of this sequence is 1 - A283071 = 0.6699019646... - Amiram Eldar, Dec 08 2020

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A020639, A088377, A067029, A283050, A283071.

Subsequences: A005117, A016825.

Programs

Haskell

a247180 n = a247180_list !! (n-1)
a247180_list = filter ((== 1) . a067029) [1..]

Mathematica

Select[Range[100],FactorInteger[#][[1,2]]==1&] (* Harvey P. Dale, Jan 29 2020 *)

PARI

isok(m) = (m>1) && (factor(m)[1,2] == 1); \\ Michel Marcus, Dec 08 2020

Formula

a(n) mod A088377(a(n)) > 0;

A067029(a(n)) = 1.