A068977 Numbers k such that Sum_{d|k} d/tau(d) is an integer, where tau(x) = A000005(x).

1, 2, 6, 10, 14, 18, 22, 26, 28, 34, 38, 46, 52, 56, 58, 62, 74, 76, 82, 86, 94, 104, 106, 118, 122, 124, 134, 142, 146, 148, 152, 158, 166, 168, 172, 178, 194, 202, 206, 208, 214, 218, 226, 244, 248, 254, 262, 268, 274, 278, 280, 292, 296, 298, 302, 312, 314

Offset

1,2

Links

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

Mathematica

Select[Range[1000], IntegerQ[Sum[k/DivisorSigma[0, k], {k, Divisors[#]}]] &] (* Vaclav Kotesovec, Mar 22 2019 *)

Prog

(PARI) isok(k) = denominator(sumdiv(k, d, d/numdiv(d))) == 1; \\ Amiram Eldar, Feb 02 2025

Crossrefs

Cf. A000005, A182463, A324503, A324504.

Sequence in context: A232176 A366047 A187884 * A251538 A111284 A130824

Adjacent sequences: A068974 A068975 A068976 * A068978 A068979 A068980

Keyword

easy,nonn,changed

Author

Benoit Cloitre, Apr 06 2002

Status

approved