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A331050
Positive integers whose number of factorizations into factors > 1 (A001055) is odd.
9
1, 2, 3, 5, 7, 8, 11, 13, 16, 17, 19, 23, 24, 27, 29, 30, 31, 32, 36, 37, 40, 41, 42, 43, 47, 53, 54, 56, 59, 60, 61, 64, 66, 67, 70, 71, 73, 78, 79, 81, 83, 84, 88, 89, 90, 96, 97, 100, 101, 102, 103, 104, 105, 107, 109, 110, 113, 114, 120, 125, 126, 127, 128
OFFSET
1,2
COMMENTS
First differs from A319239 in lacking 256.
MATHEMATICA
facs[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[facs[n/d], Min@@#>=d&]], {d, Rest[Divisors[n]]}]];
Select[Range[100], OddQ[Length[facs[#]]]&]
CROSSREFS
Complement of A331051.
The version for powers of two (instead of odds) is A330977.
The version for primes (instead of odds) is A330991.
Sequence in context: A287893 A051600 A319239 * A375960 A026410 A066720
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jan 10 2020
STATUS
approved