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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 (list; graph; refs; listen; history; text; internal format)
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 non-reversed 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

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Last modified August 8 08:27 EDT 2020. Contains 336293 sequences. (Running on oeis4.)