A124676 a(n) = largest integer < n such that the positive integers <= a(n) and coprime to a(n) are also coprime to n.

1, 2, 2, 4, 2, 6, 6, 6, 4, 10, 6, 12, 6, 3, 14, 16, 12, 18, 10, 6, 10, 22, 18, 20, 12, 24, 14, 28, 2, 30, 30, 9, 16, 5, 30, 36, 18, 12, 30, 40, 6, 42, 22, 30, 22, 46, 42, 42, 40, 15, 26, 52, 48, 10, 42, 18, 28, 58, 30, 60, 30, 42, 62, 10, 6, 66, 34, 21, 4, 70, 66, 72, 36, 60, 38, 7, 12

Offset: 2

Author

Leroy Quet, Dec 24 2006

Keywords

• nonn

Examples

			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) = the largest of these < 6, which is 2.
		

Crossrefs

Cf. A126260, A073353.

Programs

Mathematica

f[n_] := Select[Range[n], GCD[ #, n] == 1 &];g[n_] := Select[Range[n - 1], Times @@ GCD[f[ # ], n] == 1 &];Max /@ Table[g[n], {n, 2, 80}] (* Ray Chandler, Dec 24 2006 *)

Extensions

Extended by Ray Chandler, Dec 24 2006