

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
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OFFSET

1,2


COMMENTS

Unsorted prime signature (A124010) is the sequence of exponents in a number's prime factorization.


LINKS

Table of n, a(n) for n=1..77.


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 nonreversed version is A071364.
Unsorted prime signature is A124010.
Numbers whose prime signature is aperiodic are A329139.
Cf. A056239, A112798, A233249, A333217, A333219, A334032, A334033.
Sequence in context: A328707 A067824 A107067 * A320389 A046801 A316437
Adjacent sequences: A331577 A331578 A331579 * A331581 A331582 A331583


KEYWORD

nonn


AUTHOR

Gus Wiseman, Apr 18 2020


STATUS

approved



