A069084 Numbers n such that sigma(n)/tau(n) has denominator 5.

16, 48, 80, 81, 112, 176, 208, 240, 272, 336, 368, 405, 496, 528, 560, 567, 592, 624, 625, 656, 688, 720, 752, 784, 816, 848, 880, 891, 976, 1040, 1053, 1072, 1104, 1134, 1136, 1168, 1232, 1328, 1360, 1377, 1456, 1488, 1536, 1552, 1584, 1616, 1620, 1648

Offset: 1

Author

Benoit Cloitre, Apr 05 2002

Keywords

• easy
• nonn

Links

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

Crossrefs

Cf. A000005, A000203, A057021.

Programs

Magma

[n:n in [1..1700]|Denominator(SumOfDivisors(n)/#Divisors(n)) eq 5]; // Marius A. Burtea, Sep 08 2019

Mathematica

Select[Range[500], Denominator[DivisorSigma[1, #]/DivisorSigma[0, #]] == 5 &] (* Amiram Eldar, Sep 08 2019 *)

Formula

n such that A057021(n)=5