%I #11 May 05 2023 01:40:09
%S 6,12,18,24,28,30,40,42,45,48,54,56,60,66,72,78,84,90,96,102,108,112,
%T 114,120,126,132,135,138,140,144,150,156,162,168,174,180,186,192,196,
%U 198,200,204,210,216,220,222,224,225,228,234,240,246,252,258,264,270,276
%N Numbers whose set of divisors can be partitioned into disjoint parts, all of length > 1 and having integer harmonic mean.
%C Numbers k such that A362802(k) > 0.
%C Includes all the harmonic numbers (A001599) except for 1, since the set of their divisors has an integer harmonic mean (in this case the partition is into a single part).
%C This sequence is infinite. For example, if k is a term and p is a prime that does not divide k, then k*p is also a term.
%e 12 is a term since its set of divisors, {1, 2, 3, 4, 6, 12} can be partitioned into 2 disjoint parts, {1, 2, 3, 6} and {4, 12}, whose harmonic means, 2 and 6, are both integers.
%t harmQ[s_] := AllTrue[s, Length[#] > 1 && IntegerQ[HarmonicMean[#]] &]; q[n_] := Module[{d = Divisors[n], r}, r = ResourceFunction["SetPartitions"][d]; AnyTrue[r, harmQ]]; Do[If[q[n], Print[n]], {n, 1, 100}]
%Y Cf. A362802.
%Y Subsequences: A001599 \ {1}, A348715, A362803 \ {1}.
%K nonn
%O 1,1
%A _Amiram Eldar_, May 04 2023