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 A170825 a(n) is the product of the distinct primes of form 6*k-1 that divide n. 4
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 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, A170819. Cf. A140214. - R. J. Mathar, Jan 21 2010 Sequence in context: A170817 A170818 A046622 * A140214 A343431 A071020 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

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Last modified May 9 03:39 EDT 2021. Contains 343685 sequences. (Running on oeis4.)