A015632 Number of ordered triples of integers from [ 1,n ] with no common factors between pairs.

1, 2, 4, 6, 12, 14, 26, 33, 46, 52, 84, 91, 137, 152, 174, 199, 279, 295, 397, 425, 475, 513, 663, 692, 819, 876, 986, 1044, 1286, 1315, 1593, 1700, 1838, 1939, 2123, 2186, 2582, 2711, 2905, 3008, 3498, 3564, 4106, 4272, 4476, 4666, 5316, 5433, 5985

Offset: 1

Author

Olivier Gérard

Keywords

• nonn

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..500

Programs

Haskell

a015632 n = length [(x,y,z) | z <- [1..n], y <- [1..z], gcd y z == 1,
                              x <- [1..y], gcd x z == 1, gcd x y == 1]
-- Reinhard Zumkeller, Nov 14 2011

Formula

a(n) ~ k * n^3 where k is 1/6 * A065473 = 0.04779.... [Charles R Greathouse IV, Nov 14 2011]