A329879 Numbers k such that k and nusigma(k) have the same set of prime divisors, where nusigma(k) is the sum of nonunitary divisors of k (A048146).

4, 9, 24, 25, 49, 54, 112, 121, 150, 169, 289, 294, 361, 480, 529, 726, 750, 841, 961, 1014, 1369, 1681, 1734, 1849, 1984, 2058, 2166, 2209, 2430, 2520, 2688, 2809, 3174, 3481, 3721, 3780, 4489, 5041, 5046, 5329, 5760, 5766, 6241, 6889, 7921, 7986, 8214, 8700

Offset

1,1

Comments

Numbers k such that rad(nusigma(k)) = rad(k), where rad(k) is the squarefree kernel of k (A007947).

Links

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

Mathematica

rad[n_] := Times @@ (First@# & /@ FactorInteger@ n); usigma[1] = 1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); nusigma[n_] := DivisorSigma[1, n] - usigma[n]; Select[Range[10^4], rad[nusigma[#]] == rad[#] &]

Crossrefs

Cf. A007947, A027598, A048146, A329858.

Sequence in context: A288105 A288101 A320913 * A320059 A373002 A270450

Adjacent sequences: A329876 A329877 A329878 * A329880 A329881 A329882

Keyword

nonn

Author

Amiram Eldar, Nov 23 2019

Status

approved