A046683 Numbers k such that the sum of squares of divisors of k and sum of cubes of divisors of k are relatively prime.

1, 2, 4, 9, 18, 25, 36, 100, 121, 225, 289, 484, 529, 841, 900, 1089, 1156, 1681, 2116, 2209, 2601, 2809, 3364, 3481, 4356, 4761, 5041, 6724, 6889, 7225, 7569, 7921, 8836, 10201, 10404, 11236, 11449, 12769, 13225, 13924, 15129, 17161, 18769, 19044

Offset: 1

Author

Labos Elemer

Keywords

• nonn

Comments

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

Links

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

Crossrefs

Cf. A028982, A046678, A046679, A046680, A046681, A046685.

Programs

Mathematica

sdcdQ[n_]:=Module[{d=Divisors[n]},CoprimeQ[Total[d^2],Total[d^3]]]; Select[ Range[ 20000],sdcdQ] (* Harvey P. Dale, Apr 09 2018 *)

PARI

isok(n) = gcd(sigma(n, 2), sigma(n, 3)) == 1; \\ Michel Marcus, Sep 24 2019