A170825 a(n) is the product of the distinct primes of form 6*k-1 that divide n.

1, 1, 1, 1, 5, 1, 1, 1, 1, 5, 11, 1, 1, 1, 5, 1, 17, 1, 1, 5, 1, 11, 23, 1, 5, 1, 1, 1, 29, 5, 1, 1, 11, 17, 5, 1, 1, 1, 1, 5, 41, 1, 1, 11, 5, 23, 47, 1, 1, 5, 17, 1, 53, 1, 55, 1, 1, 29, 59, 5, 1, 1, 1, 1, 5, 11, 1, 17, 23, 5, 71, 1, 1, 1, 5, 1, 11, 1, 1, 5, 1, 41, 83, 1, 85, 1, 29, 11, 89, 5, 1

Offset

1,5

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

a(n) = A007947(A343431(n)) = A343431(A007947(n)). - Peter Munn, Jan 15 2022

Maple

A170825 := proc(n) a := 1 ; for p in numtheory[factorset](n) do if p mod 6 = 5 then a := a*p ; end if ; end do ; a ; end proc: seq(A170825(n), n=1..120) ; # R. J. Mathar, Jan 21 2010

Mathematica

Table[Times@@Select[Transpose[FactorInteger[n]][[1]], IntegerQ[(#+1)/6]&], {n, 100}] (* Harvey P. Dale, Nov 01 2013 *)

Prog

(PARI) a(n) = my(f=factor(n)); for(i=1, #f~, f[i, 2] = (f[i, 1]%6)==5); factorback(f); \\ Michel Marcus, Sep 30 2020

Crossrefs

Cf. A007528, A007947, A170819, A343431.

Cf. A140214. - R. J. Mathar, Jan 21 2010

Sequence in context: A170817 A170818 A046622 * A140214 A343431 A366374

Adjacent sequences: A170822 A170823 A170824 * A170826 A170827 A170828

Keyword

nonn,mult,easy

Author

N. J. A. Sloane, Dec 25 2009, following a suggestion from Jonathan Vos Post

Extensions

More terms from R. J. Mathar, Jan 21 2010

Status

approved