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A340689
Numbers with a factorization of length 2^k into factors > 1, where k is the greatest factor.
5
1, 16, 384, 576, 864, 1296, 1944, 2916, 4374, 6561, 131072, 196608, 262144, 294912, 393216, 442368, 524288, 589824, 663552, 786432, 884736, 995328, 1048576, 1179648, 1327104, 1492992, 1572864, 1769472, 1990656, 2097152, 2239488, 2359296, 2654208, 2985984, 3145728
OFFSET
1,2
EXAMPLE
The initial terms and a valid factorization of each are:
1 =
16 = 2*2*2*2
384 = 2*2*2*2*2*2*2*3
576 = 2*2*2*2*2*2*3*3
864 = 2*2*2*2*2*3*3*3
1296 = 2*2*2*2*3*3*3*3
1944 = 2*2*2*3*3*3*3*3
2916 = 2*2*3*3*3*3*3*3
4374 = 2*3*3*3*3*3*3*3
6561 = 3*3*3*3*3*3*3*3
131072 = 2*2*2*2*2*2*2*2*2*2*2*2*2*2*2*4
196608 = 2*2*2*2*2*2*2*2*2*2*2*2*2*2*3*4
262144 = 2*2*2*2*2*2*2*2*2*2*2*2*2*2*4*4
294912 = 2*2*2*2*2*2*2*2*2*2*2*2*2*3*3*4
MATHEMATICA
facs[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[facs[n/d], Min@@#>=d&]], {d, Rest[Divisors[n]]}]];
Select[Range[1000], Select[facs[#], Length[#]==2^Max@@#&]!={}&]
CROSSREFS
Partitions of the prescribed type are counted by A340611.
The conjugate version is A340690.
A001055 counts factorizations, with strict case A045778.
A047993 counts balanced partitions.
A316439 counts factorizations by product and length.
A340596 counts co-balanced factorizations.
A340597 lists numbers with an alt-balanced factorization.
A340653 counts balanced factorizations.
Sequence in context: A189766 A235442 A343213 * A302262 A302962 A302805
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jan 28 2021
EXTENSIONS
More terms from Chai Wah Wu, Feb 01 2021
STATUS
approved