A074838 Numbers m such that sum(d|m, 1/core(d) ) is an integer where core(x) is the squarefree part of x.

1, 6, 8, 16, 20, 24, 54, 60, 72, 96, 126, 128, 180, 216, 243, 256, 384, 441, 486, 500, 504, 540, 648, 704, 729, 864, 891, 972, 1100, 1152, 1260, 1500, 1536, 1620, 1782, 1792, 1944, 2016, 2048, 2112, 2205, 2560, 3300, 3456, 3528, 3564, 3645, 3888, 4096

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..1000

Mathematica

f[p_, e_] := If[OddQ[e], p, 1]; sqf[n_] := Times @@ (f @@@ FactorInteger[n]); seqQ[n_] := IntegerQ @ DivisorSum[n, 1/sqf[#] &]; Select[Range[2^12], seqQ] (* Amiram Eldar, Apr 02 2020 *)

Prog

(PARI) isok(m) = denominator(sumdiv(m, d, 1/core(d))) == 1; \\ Michel Marcus, Apr 02 2020

Crossrefs

Cf. A007913.

Sequence in context: A315934 A315935 A315936 * A315937 A315938 A315939

Adjacent sequences: A074835 A074836 A074837 * A074839 A074840 A074841

Keyword

nonn

Author

Benoit Cloitre, Sep 09 2002

Status

approved