[go: up one dir, main page]

login
A340690
Numbers with a factorization whose greatest factor is 2^k, where k is the number of factors.
4
2, 8, 12, 16, 32, 48, 64, 72, 80, 96, 112, 120, 128, 144, 160, 168, 192, 200, 224, 240, 256, 280, 288, 320, 336, 384, 392, 432, 448, 480, 512, 576, 640, 672, 704, 720, 768, 800, 832, 864, 896, 960, 1008, 1024, 1056, 1120, 1152, 1200, 1248, 1280, 1296, 1344
OFFSET
1,1
EXAMPLE
The initial terms and a valid factorization of each:
2 = 2 168 = 3*7*8 512 = 2*2*2*2*32
8 = 2*4 192 = 2*2*3*16 576 = 2*2*9*16
12 = 3*4 200 = 5*5*8 640 = 2*2*10*16
16 = 4*4 224 = 4*7*8 672 = 2*3*7*16
32 = 2*2*8 240 = 5*6*8 704 = 2*2*11*16
48 = 2*3*8 256 = 2*2*4*16 720 = 3*3*5*16
64 = 2*4*8 280 = 5*7*8 768 = 2*2*2*3*32
72 = 3*3*8 288 = 2*3*3*16 800 = 2*5*5*16
80 = 2*5*8 320 = 2*2*5*16 832 = 2*2*13*16
96 = 2*6*8 336 = 6*7*8 864 = 2*3*9*16
112 = 2*7*8 384 = 2*2*6*16 896 = 2*2*14*16
120 = 3*5*8 392 = 7*7*8 960 = 2*2*15*16
128 = 2*2*2*16 432 = 3*3*3*16 1008 = 3*3*7*16
144 = 3*6*8 448 = 2*2*7*16 1024 = 2*2*2*4*32
160 = 4*5*8 480 = 2*3*5*16 1056 = 2*3*11*16
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[#], 2^Length[#]==Max@@#&]!={}&]
CROSSREFS
Partitions of the prescribed type are counted by A340611.
The conjugate version is A340689.
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: A067884 A005880 A290608 * A303900 A046470 A090772
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jan 28 2021
STATUS
approved