A046754 Numbers k such that the square of d(k) (number of divisors) divides k.

1, 9, 128, 625, 972, 1152, 2000, 2025, 5625, 6561, 7776, 8100, 10000, 10800, 18000, 21952, 26244, 30000, 32768, 35721, 50625, 55296, 56700, 64000, 64800, 65856, 70000, 80000, 84672, 89100, 90000, 97200, 98304, 99225, 105300, 109760, 110000

Offset

1,2

Comments

Subset of A033950.

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Donovan Johnson)

Example

If k = 972, d(k) = sigma(0,k) = 18. Its square is 324 which divides 972.

Mathematica

Select[Range[110000], IntegerQ[#/DivisorSigma[0, #]^2] &] (* Jayanta Basu, Jun 28 2013 *)

Crossrefs

Cf. A033950, A046755, A046756.

Sequence in context: A362776 A365033 A073014 * A203425 A275259 A064746

Adjacent sequences: A046751 A046752 A046753 * A046755 A046756 A046757

Keyword

nonn

Author

Labos Elemer

Status

approved