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A326028
Number of factorizations of n into factors > 1 with integer geometric mean.
25
0, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 5, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 8, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 1, 1, 1
OFFSET
1,4
COMMENTS
First differs from A294336 and A316782 at a(36) = 5.
FORMULA
a(2^n) = A067538(n).
EXAMPLE
The a(4) = 2 through a(36) = 5 factorizations (showing only the cases where n is a perfect power).
(4) (8) (9) (16) (25) (27) (32) (36)
(2*2) (2*2*2) (3*3) (2*8) (5*5) (3*3*3) (2*2*2*2*2) (4*9)
(4*4) (6*6)
(2*2*2*2) (2*18)
(3*12)
MATHEMATICA
facs[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[facs[n/d], Min@@#>=d&]], {d, Rest[Divisors[n]]}]];
Table[Length[Select[facs[n], IntegerQ[GeometricMean[#]]&]], {n, 2, 100}]
CROSSREFS
Positions of terms > 1 are the perfect powers A001597.
Partitions with integer geometric mean are A067539.
Subsets with integer geometric mean are A326027.
Factorizations with integer average and geometric mean are A326647.
Sequence in context: A294336 A316782 A326647 * A294338 A316790 A316789
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jul 15 2019
STATUS
approved