A069166 Numbers k such that k*Sum_{d|k} 1/sigma(d) is an integer.

1, 6, 14, 40, 120, 244, 280, 440, 494, 680, 920, 1220, 2040, 2840, 2968, 3480, 6360, 9880, 10680, 16376, 20618, 25160, 32280, 34720, 40136, 40280, 42136, 45560, 45994, 46280, 85880, 91160, 120408, 200680, 213280, 231080, 242840, 377080, 410552, 412360, 421480, 441496, 447320

Offset: 1

Author

Benoit Cloitre, Apr 09 2002

Keywords

• easy
• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..300

Crossrefs

Cf. A069164.

Programs

Mathematica

Select[Range[125000],IntegerQ[# Total[1/DivisorSigma[1,Divisors[#]]]]&] (* Harvey P. Dale, Nov 03 2017 *)

PARI

isok(k) = denominator(k*sumdiv(k, d, 1/sigma(d))) == 1; \\ Michel Marcus, Feb 15 2021

Extensions

More terms from Michel Marcus, Feb 15 2021