

A335510


Number of (1,1,1)matching permutations of the prime indices of n.


5



0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 5, 0, 0, 0, 0, 0, 4, 0, 4, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 10, 0, 0, 0, 0, 0, 0, 0, 5, 1, 0, 0, 0, 0, 0, 0
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OFFSET

1,24


COMMENTS

A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
We define a pattern to be a finite sequence covering an initial interval of positive integers. Patterns are counted by A000670 and ranked by A333217. A sequence S is said to match a pattern P if there is a not necessarily contiguous subsequence of S whose parts have the same relative order as P. For example, (3,1,1,3) matches (1,1,2), (2,1,1), and (2,1,2), but avoids (1,2,1), (1,2,2), and (2,2,1).


LINKS

Table of n, a(n) for n=1..87.
Wikipedia, Permutation pattern
Gus Wiseman, Sequences counting and ranking compositions by the patterns they match or avoid.


FORMULA

If n is cubefree, a(n) = 0; otherwise a(n) = A008480(n).


MATHEMATICA

primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Table[Length[Select[Permutations[primeMS[n]], MatchQ[#, {___, x_, ___, x_, ___, x_, ___}]&]], {n, 0, 100}]


CROSSREFS

Patterns matching this pattern are counted by A335508.
These compositions are counted by A335455.
The (1,1)matching version is A335487.
The complement A335511 is the avoiding version.
These permutations are ranked by A335512.
Permutations of prime indices are counted by A008480.
Patterns are counted by A000670 and ranked by A333217.
Antirun permutations of prime indices are counted by A335452.
Cf. A056239, A056986, A112798, A238279, A281188, A333221, A333755, A335456, A335460, A335462, A335463.
Sequence in context: A258649 A258650 A156393 * A331438 A215061 A215060
Adjacent sequences: A335507 A335508 A335509 * A335511 A335512 A335513


KEYWORD

nonn


AUTHOR

Gus Wiseman, Jun 19 2020


STATUS

approved



