A046681 Numbers k such that the number of divisors of k and sum of 4th powers of divisors of k are relatively prime.

1, 2, 8, 9, 18, 64, 72, 128, 625, 729, 1024, 1152, 1250, 1458, 4096, 5000, 5625, 5832, 6561, 8192, 9216, 11250, 13122, 15625, 31250, 32768, 40000, 45000, 46656, 52488, 59049, 65536, 80000, 93312, 117649, 118098, 125000, 235298, 262144, 294912

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..5000

Mathematica

Select[Range[300000], CoprimeQ[DivisorSigma[0, #], DivisorSigma[4, #]]&] (* Harvey P. Dale, May 30 2012 *)

Prog

(PARI) isok(n) = gcd(sigma(n, 4), numdiv(n)) == 1; \\ Michel Marcus, Sep 24 2019

Crossrefs

Cf. A028982, A046678, A046679, A046680, A046683, A046685.

Sequence in context: A118962 A096033 A073413 * A259672 A163619 A166968

Adjacent sequences: A046678 A046679 A046680 * A046682 A046683 A046684

Keyword

nonn

Author

Labos Elemer

Status

approved