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A140211
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a(n) = Product_{d == 3 (mod 4) and d|n} d.
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3
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1, 1, 3, 1, 1, 3, 7, 1, 3, 1, 11, 3, 1, 7, 45, 1, 1, 3, 19, 1, 21, 11, 23, 3, 1, 1, 81, 7, 1, 45, 31, 1, 33, 1, 245, 3, 1, 19, 117, 1, 1, 21, 43, 11, 45, 23, 47, 3, 7, 1, 153, 1, 1, 81, 605, 7, 57, 1, 59, 45, 1, 31, 1323, 1, 1, 33, 67, 1, 69, 245, 71, 3, 1, 1, 3375, 19, 77, 117, 79, 1, 81, 1
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OFFSET
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1,3
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LINKS
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FORMULA
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MAPLE
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a := 1;
for d in numtheory[divisors](n) do
if modp(d, 4) = 3 then
a := a*d ;
end if;
end do:
a;
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MATHEMATICA
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ListProduct[lst_] := Fold[Times, 1, lst] lst = {}; For[n = 1, n <= 1000, n++, AppendTo[lst, ListProduct[Select[Divisors[n], Mod[ #, 4] == 3 &]]]] lst (* Jasper Mulder (jasper.mulder(AT)planet.nl), Jul 15 2009 *)
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PROG
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(PARI) a(n) = my(p=1); fordiv(n, d, if ((d % 4)==3, p*=d)); p; \\ Michel Marcus, Jan 07 2021
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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