A069081 Numbers n such that sigma(n)/tau(n) has denominator 2.

2, 10, 18, 24, 26, 32, 34, 50, 58, 74, 82, 88, 90, 98, 106, 120, 122, 130, 146, 152, 160, 170, 178, 194, 202, 216, 218, 226, 234, 242, 250, 274, 288, 290, 298, 306, 312, 314, 338, 344, 346, 362, 370, 386, 394, 408, 410, 416, 440, 442, 458, 466, 472, 482, 490

Offset

1,1

Links

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

Formula

n such that A057021(n)=2.

Mathematica

Select[Range[500], Denominator[DivisorSigma[1, #]/DivisorSigma[0, #]] == 2 &] (* Amiram Eldar, Sep 08 2019 *)

Prog

(Magma) [n:n in [1..500]|Denominator(SumOfDivisors(n)/#Divisors(n)) eq 2]; // Marius A. Burtea, Sep 08 2019

Crossrefs

Cf. A000005, A000203, A057021.

Sequence in context: A341032 A082939 A074069 * A126005 A017089 A097269

Adjacent sequences: A069078 A069079 A069080 * A069082 A069083 A069084

Keyword

easy,nonn

Author

Benoit Cloitre, Apr 05 2002

Status

approved