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A170819
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a(n) = product of distinct primes of the form 4k-1 that divide n.
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5
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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
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OFFSET
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1,3
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COMMENTS
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Multiplicative with a(p^e) = p*A011765(p+1), e > 0. - R. J. Mathar, Jun 07 2011
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LINKS
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Michael De Vlieger, Table of n, a(n) for n = 1..10000
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MAPLE
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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
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MATHEMATICA
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Array[Times @@ Select[FactorInteger[#][[All, 1]], Mod[#, 4] == 3 &] &, 85] (* Michael De Vlieger, Feb 19 2019 *)
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PROG
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(PARI) for(n=1, 99, t=select(x->x%4==3, factor(n)[, 1]); print1(prod(i=1, #t, t[i])", "))
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CROSSREFS
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Cf. A170817-A170818, A097706, A083025, A007947.
Sequence in context: A161788 A345468 A351518 * A140211 A248101 A097706
Adjacent sequences: A170816 A170817 A170818 * A170820 A170821 A170822
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KEYWORD
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nonn,mult
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AUTHOR
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N. J. A. Sloane, Dec 23 2009
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EXTENSIONS
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Extended with PARI program by M. F. Hasler, Dec 23 2009
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STATUS
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approved
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