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A170819
a(n) = product of distinct primes of the form 4k-1 that divide n.
6
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
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])", "))
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