A046686 Numbers k such that k and sum of cubes of divisors of k are relatively prime.

1, 2, 3, 4, 5, 7, 8, 9, 11, 13, 16, 17, 19, 23, 25, 27, 29, 31, 32, 36, 37, 39, 41, 43, 47, 49, 50, 53, 55, 57, 59, 61, 63, 64, 65, 67, 71, 73, 75, 77, 79, 81, 83, 85, 89, 93, 97, 98, 100, 101, 103, 107, 109, 111, 113, 115, 117, 121, 125, 127, 128, 129, 131, 137, 139, 143

Offset

1,2

Comments

All even terms are either squares or doubled squares. - Ivan Neretin, Dec 30 2015

The asymptotic density of this sequence is 0 (Dressler, 1974). - Amiram Eldar, Jul 23 2020

Links

Ivan Neretin, Table of n, a(n) for n = 1..10000

Robert E. Dressler, On a theorem of Niven, Canadian Mathematical Bulletin, Vol. 17, No. 1 (1974), pp. 109-110.

Mathematica

Select[Range[143], GCD[#, DivisorSigma[3, #]] == 1 &] (* Ivan Neretin, Dec 30 2015 *)

Crossrefs

Cf. A001158, A046684, A046687.

Sequence in context: A326847 A298538 A326534 * A137944 A359390 A323306

Adjacent sequences: A046683 A046684 A046685 * A046687 A046688 A046689

Keyword

nonn

Author

Labos Elemer

Status

approved