A124443 a(1)=1, a(n) = LCM of the integers, from 1 to n/2, which are coprime to n.

1, 1, 1, 1, 2, 1, 6, 3, 4, 3, 60, 5, 60, 15, 28, 105, 840, 35, 2520, 63, 40, 315, 27720, 385, 5544, 3465, 40040, 6435, 360360, 1001, 360360, 45045, 7280, 45045, 350064, 85085, 12252240, 765765, 1989680, 2909907, 232792560, 230945, 232792560, 1322685

Offset: 1

Author

Leroy Quet, Nov 01 2006

Keywords

• nonn

Examples

			The integers which are >= 1 and are <= 9/2 and which are coprime to 9 are 1, 2 and 4. So a(9) = lcm(1,2,4) = 4.
		

Crossrefs

Cf. A124444.

Programs

Mathematica

f[n_] := If[n == 1, 1, LCM @@ Select[Range[Floor[n/2]], GCD[ #, n] == 1 &]];Table[f[n], {n, 45}] (* Ray Chandler, Nov 12 2006 *)

PARI

a(n) = lcm(select(x->(gcd(x, n)==1), vector(n\2, k, k))); \\ Michel Marcus, Mar 18 2018

Extensions

Extended by Ray Chandler, Nov 12 2006