A046679 Numbers k such that the number of divisors of k and sum of squares of divisors of k are relatively prime.

1, 2, 8, 9, 16, 18, 64, 72, 81, 128, 144, 625, 729, 1024, 1152, 1296, 1458, 2401, 4096, 5184, 5625, 5832, 6561, 8192, 9216, 10000, 11664, 13122, 15625, 21609, 28561, 31250, 32768, 38416, 40000, 46656, 50625, 52488, 59049, 65536, 83521, 90000

Offset

1,2

Comments

It can be shown that this is a subsequence of A028982.

Links

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

Mathematica

Select[Range[91000], CoprimeQ[DivisorSigma[0, #], DivisorSigma[2, #]]&] (* Harvey P. Dale, May 11 2011 *)

Prog

(PARI) isok(n) = gcd(sigma(n, 2), numdiv(n)) == 1; \\ Michel Marcus, Sep 24 2019

Crossrefs

Cf. A028982, A046678, A046680, A046681, A046683, A046685.

Sequence in context: A056805 A226825 A367984 * A004999 A105125 A230314

Adjacent sequences: A046676 A046677 A046678 * A046680 A046681 A046682

Keyword

nonn

Author

Labos Elemer

Extensions

a(1)=1 added by Amiram Eldar, Sep 24 2019

Status

approved