A170819 a(n) = product of distinct primes of the form 4k-1 that divide n.

1, 1, 3, 1, 1, 3, 7, 1, 3, 1, 11, 3, 1, 7, 3, 1, 1, 3, 19, 1, 21, 11, 23, 3, 1, 1, 3, 7, 1, 3, 31, 1, 33, 1, 7, 3, 1, 19, 3, 1, 1, 21, 43, 11, 3, 23, 47, 3, 7, 1, 3, 1, 1, 3, 11, 7, 57, 1, 59, 3, 1, 31, 21, 1, 1, 33, 67, 1, 69, 7, 71, 3, 1, 1, 3, 19, 77, 3, 79, 1, 3, 1, 83, 21, 1

Offset

1,3

Links

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Formula

Multiplicative with a(p^e) = p^A011765(p+1), e > 0. - R. J. Mathar, Jun 07 2011

a(n) = A007947(A097706(n)) = A097706(A007947(n)). - Peter Munn, Jul 06 2023

Maple

A170819 := proc(n) a := 1 ; for p in numtheory[factorset](n) do if p mod 4 = 3 then a := a*p ; end if; end do: a ; end proc:
seq(A170819(n), n=1..20) ; # R. J. Mathar, Jun 07 2011

Mathematica

Array[Times @@ Select[FactorInteger[#][[All, 1]], Mod[#, 4] == 3 &] &, 85] (* Michael De Vlieger, Feb 19 2019 *)

Prog

(PARI) for(n=1, 99, t=select(x->x%4==3, factor(n)[, 1]); print1(prod(i=1, #t, t[i])", "))

Crossrefs

Cf. A007947, A011765, A065339, A097706, A170817, A170818, A363340.

Sequence in context: A161788 A345468 A351518 * A140211 A248101 A097706

Adjacent sequences: A170816 A170817 A170818 * A170820 A170821 A170822

Keyword

nonn,mult

Author

N. J. A. Sloane, Dec 23 2009

Extensions

Extended with PARI program by M. F. Hasler, Dec 23 2009

Status

approved