A329239 Numbers k such that the sum of unitary divisors of k is a cube.

1, 7, 102, 110, 120, 142, 159, 184, 187, 381, 588, 684, 690, 714, 770, 796, 840, 931, 994, 1034, 1054, 1065, 1113, 1128, 1173, 1240, 1265, 1288, 1293, 1309, 1528, 1633, 1643, 2619, 2667, 3638, 3937, 4280, 4505, 4664, 4788, 4830, 4855, 5176, 5572, 5671, 5730

Offset

1,2

Links

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

Example

7 is a term since usigma(7) = 8 = 2^3, where usigma is A034448.
102 is a term since usigma(102) = 216 = 6^3.

Mathematica

usigma[1] = 1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); Select[Range[10000], IntegerQ @ Surd[usigma [#], 3] &]

Prog

(PARI) isok(m) = ispower(sumdiv(m, d, if(gcd(d, m/d)==1, d)), 3); \\ Michel Marcus, Mar 15 2020

Crossrefs

The unitary version of A020477.

Cf. A000578, A034448, A063937, A333258.

Sequence in context: A367137 A367152 A357334 * A020477 A348887 A358159

Adjacent sequences: A329236 A329237 A329238 * A329240 A329241 A329242

Keyword

nonn

Author

Amiram Eldar, Mar 13 2020

Status

approved