%I
%S 1,6,8,16,20,24,54,60,72,96,126,128,180,216,243,256,384,441,486,500,
%T 504,540,648,704,729,864,891,972,1100,1152,1260,1500,1536,1620,1782,
%U 1792,1944,2016,2048,2112,2205,2560,3300,3456,3528,3564,3645,3888,4096
%N Numbers m such that sum(dm, 1/core(d) ) is an integer where core(x) is the squarefree part of x.
%H Amiram Eldar, <a href="/A074838/b074838.txt">Table of n, a(n) for n = 1..1000</a>
%t 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 *)
%o (PARI) isok(m) = denominator(sumdiv(m, d, 1/core(d))) == 1; \\ _Michel Marcus_, Apr 02 2020
%Y Cf. A007913.
%K nonn
%O 1,2
%A _Benoit Cloitre_, Sep 09 2002
