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A327907
Numbers with more than one factorization into at factors > 1 with integer mean.
2
4, 8, 9, 12, 15, 16, 20, 21, 24, 25, 27, 28, 32, 33, 35, 36, 39, 40, 42, 44, 45, 48, 49, 50, 51, 52, 54, 55, 56, 57, 60, 63, 64, 65, 68, 69, 72, 75, 76, 77, 78, 80, 81, 84, 85, 87, 88, 91, 92, 93, 95, 96, 99, 100, 104, 105, 108, 110, 111, 112, 114, 115, 116
OFFSET
1,1
EXAMPLE
There are 6 factorizations of 60 with integer mean, namely:
(60)
(2*30)
(6*10)
(3*4*5)
(2*3*10)
(2*2*3*5)
so 60 is in the sequence.
MATHEMATICA
facs[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[facs[n/d], Min@@#>=d&]], {d, Rest[Divisors[n]]}]];
Select[Range[100], Length[Select[facs[#], IntegerQ[Mean[#]]&]]>1&]
CROSSREFS
Complement of A327906.
Positions of terms > 1 in A326622.
Sequence in context: A037973 A044844 A145190 * A177713 A235992 A362006
KEYWORD
nonn
AUTHOR
Gus Wiseman, Sep 30 2019
STATUS
approved