The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 (list; graph; refs; listen; history; text; internal format)
 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 Wikipedia, Permutation pattern 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. Anti-run 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 13 17:14 EDT 2021. Contains 345008 sequences. (Running on oeis4.)