A124675 - OEIS

A124675

a(n) = product of the positive integers k, k<= n, such that the positive integers <= k and coprime to k are also coprime to n.

1, 2, 6, 8, 120, 12, 5040, 384, 324, 80, 39916800, 144, 6227020800, 672, 90, 10321920, 355687428096000, 2592, 121645100408832000, 1600, 756, 84480, 25852016738884976640000, 62208, 9000000, 1198080, 14285134080, 18816

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..28.

EXAMPLE

The positive integers k, k <= 6, where the positive integers <= k and coprime to k are also coprime to 6, are 1,2,6. So a(6) = 1*2*6 = 12.

MATHEMATICA

f[n_] := Select[Range[n], GCD[ #, n] == 1 &]; g[n_] := Select[Range[n], Times @@ GCD[f[ # ], n] == 1 &]; Times @@@ Table[g[n], {n, 30}] (* Ray Chandler, Dec 24 2006 *)

CROSSREFS

Cf. A126260, A124611.

Sequence in context: A100621 A002176 A329812 * A279258 A120709 A002689

Adjacent sequences: A124672 A124673 A124674 * A124676 A124677 A124678

KEYWORD

nonn

AUTHOR

Leroy Quet, Dec 24 2006

EXTENSIONS

Extended by Ray Chandler, Dec 24 2006

STATUS

approved