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A331580
Smallest number whose unsorted prime signature is the reversed unsorted prime signature of n.
3
1, 2, 2, 4, 2, 6, 2, 8, 4, 6, 2, 18, 2, 6, 6, 16, 2, 12, 2, 18, 6, 6, 2, 54, 4, 6, 8, 18, 2, 30, 2, 32, 6, 6, 6, 36, 2, 6, 6, 54, 2, 30, 2, 18, 18, 6, 2, 162, 4, 12, 6, 18, 2, 24, 6, 54, 6, 6, 2, 150, 2, 6, 18, 64, 6, 30, 2, 18, 6, 30, 2, 108, 2, 6, 12, 18, 6
OFFSET
1,2
COMMENTS
Unsorted prime signature (A124010) is the sequence of exponents in a number's prime factorization.
EXAMPLE
The prime signature of 12345678 = 2*3*3*47*14593 is (1,2,1,1), and the least number with prime signature (1,1,2,1) is 1050 = 2*3*5*5*7, so a(12345678) = 1050.
MATHEMATICA
ptnToNorm[y_]:=Join@@Table[ConstantArray[i, y[[i]]], {i, Length[y]}];
Table[Times@@Prime/@ptnToNorm[Reverse[Last/@If[n==1, {}, FactorInteger[n]]]], {n, 100}]
CROSSREFS
The range is A055932.
The non-reversed version is A071364.
Unsorted prime signature is A124010.
Numbers whose prime signature is aperiodic are A329139.
Sequence in context: A067824 A347458 A107067 * A320389 A046801 A348717
KEYWORD
nonn
AUTHOR
Gus Wiseman, Apr 18 2020
STATUS
approved