cp's OEIS Frontend

A331580 Smallest number whose unsorted prime signature is the reversed unsorted prime signature of n.

%I A331580 #6 Apr 19 2020 07:53:44
%S A331580 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,
%T A331580 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,
%U A331580 150,2,6,18,64,6,30,2,18,6,30,2,108,2,6,12,18,6
%N A331580 Smallest number whose unsorted prime signature is the reversed unsorted prime signature of n.
%C A331580 Unsorted prime signature (A124010) is the sequence of exponents in a number's prime factorization.
%e A331580 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.
%t A331580 ptnToNorm[y_]:=Join@@Table[ConstantArray[i,y[[i]]],{i,Length[y]}];
%t A331580 Table[Times@@Prime/@ptnToNorm[Reverse[Last/@If[n==1,{},FactorInteger[n]]]],{n,100}]
%Y A331580 The range is A055932.
%Y A331580 The non-reversed version is A071364.
%Y A331580 Unsorted prime signature is A124010.
%Y A331580 Numbers whose prime signature is aperiodic are A329139.
%Y A331580 Cf. A056239, A112798, A233249, A333217, A333219, A334032, A334033.
%K A331580 nonn
%O A331580 1,2
%A A331580 _Gus Wiseman_, Apr 18 2020