A140213 Product_{h|n and h mod 6 = 1} h; product of divisors of n of the form 6*k + 1.

1, 1, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 13, 7, 1, 1, 1, 1, 19, 1, 7, 1, 1, 1, 25, 13, 1, 7, 1, 1, 31, 1, 1, 1, 7, 1, 37, 19, 13, 1, 1, 7, 43, 1, 1, 1, 1, 1, 343, 25, 1, 13, 1, 1, 55, 7, 19, 1, 1, 1, 61, 31, 7, 1, 13, 1, 67, 1, 1, 7, 1, 1, 73, 37, 25, 19, 7, 13, 79, 1, 1, 1, 1, 7, 85, 43, 1, 1, 1, 1, 8281

Offset: 1

Author

R. J. Mathar, Jun 27 2008

Keywords

• nonn
• easy
• look

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10001

Crossrefs

Cf. A170824, A248909, A279060.

Programs

Maple

A140213 := proc(n)
    a := 1;
    for d in numtheory[divisors](n) do
        if modp(d,6) = 1 then
            a := a*d ;
        end if;
    end do:
    a;
end proc: # R. J. Mathar, Dec 15 2015

PARI

A140213(n) = { my(m=1); fordiv(n, d, if(1==(d%6), m *= d)); (m); }; \\ Antti Karttunen, Jul 09 2017

Extensions

More terms from D. S. McNeil, Mar 24 2009