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 A170819 a(n) = product of distinct primes of the form 4k-1 that divide n. 5
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Multiplicative with a(p^e) = p*A011765(p+1), e > 0. - R. J. Mathar, Jun 07 2011 LINKS Michael De Vlieger, Table of n, a(n) for n = 1..10000 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. A170817-A170818, A097706, A083025, A007947. Sequence in context: A058735 A107294 A161788 * 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

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Last modified May 9 05:11 EDT 2021. Contains 343688 sequences. (Running on oeis4.)