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A336570
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Number of maximal sets of proper divisors d|n, d < n, all belonging to A130091 (numbers with distinct prime multiplicities) and forming a divisibility chain.
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8
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1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 2, 1, 2, 2, 1, 1, 2, 1, 2, 2, 2, 1, 3, 1, 2, 1, 2, 1, 3, 1, 1, 2, 2, 2, 4, 1, 2, 2, 3, 1, 3, 1, 2, 2, 2, 1, 4, 1, 2, 2, 2, 1, 3, 2, 3, 2, 2, 1, 4, 1, 2, 2, 1, 2, 3, 1, 2, 2, 3, 1, 5, 1, 2, 2, 2, 2, 3, 1, 4, 1, 2, 1, 4, 2, 2, 2
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OFFSET
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1,6
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COMMENTS
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A number's prime signature (row n of A124010) is the sequence of positive exponents in its prime factorization, so a number has distinct prime multiplicities iff all the exponents in its prime signature are distinct.
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LINKS
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EXAMPLE
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The a(n) sets for n = 36, 120, 144, 180 (ones not shown):
{2,18} {3,12,24} {2,18,72} {2,18}
{3,12} {5,20,40} {3,9,18,72} {3,12}
{2,4,12} {2,4,8,24} {3,12,24,48} {5,20}
{3,9,18} {2,4,8,40} {3,12,24,72} {5,45}
{2,4,12,24} {2,4,8,16,48} {2,4,12}
{2,4,20,40} {2,4,8,24,48} {2,4,20}
{2,4,8,24,72} {3,9,18}
{2,4,12,24,48} {3,9,45}
{2,4,12,24,72}
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MATHEMATICA
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strsigQ[n_]:=UnsameQ@@Last/@FactorInteger[n];
fasmax[y_]:=Complement[y, Union@@(Most[Subsets[#]]&/@y)];
strses[n_]:=If[n==1, {{}}, Join@@Table[Append[#, d]&/@strses[d], {d, Select[Most[Divisors[n]], strsigQ]}]];
Table[Length[fasmax[strses[n]]], {n, 100}]
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CROSSREFS
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A336569 is the version for chains containing n.
A336571 is the non-maximal version.
A007425 counts divisors of divisors.
A045778 counts strict factorizations.
A071625 counts distinct prime multiplicities.
A074206 counts strict chains of divisors from n to 1.
A130091 lists numbers with distinct prime multiplicities.
A181796 counts divisors with distinct prime multiplicities.
Cf. A002033, A005117, A098859, A118914, A124010, A305149, A327498, A327523, A336414, A336423, A336425, A336568.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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