A277334 Numbers n, that apart from 2 are all odd and for which n/(largest prime dividing n) is squarefree.

1, 2, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 29, 31, 33, 35, 37, 39, 41, 43, 47, 49, 51, 53, 55, 57, 59, 61, 65, 67, 69, 71, 73, 75, 77, 79, 83, 85, 87, 89, 91, 93, 95, 97, 101, 103, 105, 107, 109, 111, 113, 115, 119, 121, 123, 127, 129, 131, 133, 137, 139, 141, 143, 145, 147, 149, 151, 155, 157, 159, 161, 163, 165, 167, 169

Offset: 1

Author

Antti Karttunen, Oct 12 2016

Keywords

• nonn

Comments

In other words, after 1 and 2, such odd numbers that only the largest prime factor in their prime factorization may have exponent 1 or 2, while all lesser prime factors occur at most once.

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10000

Crossrefs

Disjoint union of A056911 and A129598(A056911(n)).

Cf. A005117, A008683, A052126.

Cf. A277332 (permutation of this sequence).

Differs from A091377 for the first time at n=36, where a(36)=75, while A091377(36)=77.

Programs

Maple

with(numtheory): A277334_list := n -> seq(`if`(i=2 or (i::odd and issqrfree(i/ max(factorset(i)))),i,NULL),i=1..n): A277334_list(169); # Peter Luschny, Oct 23 2016