

A336500


Number of divisors dn with distinct prime multiplicities such that the quotient n/d also has distinct prime multiplicities.


24



1, 2, 2, 3, 2, 2, 2, 4, 3, 2, 2, 4, 2, 2, 2, 5, 2, 4, 2, 4, 2, 2, 2, 6, 3, 2, 4, 4, 2, 0, 2, 6, 2, 2, 2, 6, 2, 2, 2, 6, 2, 0, 2, 4, 4, 2, 2, 8, 3, 4, 2, 4, 2, 6, 2, 6, 2, 2, 2, 4, 2, 2, 4, 7, 2, 0, 2, 4, 2, 0, 2, 8, 2, 2, 4, 4, 2, 0, 2, 8, 5, 2, 2, 4, 2, 2, 2
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OFFSET

1,2


COMMENTS

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.


LINKS

Table of n, a(n) for n=1..87.


EXAMPLE

The a(1) = 1 through a(16) = 5 divisors:
1 1 1 1 1 2 1 1 1 2 1 1 1 2 3 1
2 3 2 5 3 7 2 3 5 11 3 13 7 5 2
4 4 9 4 4
8 12 8
16


MATHEMATICA

Table[Length[Select[Divisors[n], UnsameQ@@Last/@FactorInteger[#]&&UnsameQ@@Last/@FactorInteger[n/#]&]], {n, 25}]


CROSSREFS

A336419 is the version for superprimorials.
A336568 gives positions of zeros.
A336869 is the restriction to factorials.
A007425 counts divisors of divisors.
A056924 counts divisors greater than their quotient.
A074206 counts chains of divisors from n to 1.
A130091 lists numbers with distinct prime exponents.
A181796 counts divisors with distinct prime multiplicities.
A336424 counts factorizations using A130091.
A336422 counts divisible pairs of divisors, both in A130091.
A327498 gives the maximum divisor with distinct prime multiplicities.
A336423 counts chains in A130091, with maximal version A336569.
A336568 gives numbers not a product of two elements of A130091.
A336571 counts divisor sets using A130091, with maximal version A336570.
Cf. A000005, A001055, A002033, A098859, A124010, A167865, A253249, A336870.
Sequence in context: A161189 A328162 A067132 * A328401 A207666 A151613
Adjacent sequences: A336497 A336498 A336499 * A336501 A336502 A336503


KEYWORD

nonn


AUTHOR

Gus Wiseman, Aug 06 2020


STATUS

approved



