A074930 Number of integers in {1, 2, ..., n!} that are coprime to n.

1, 1, 4, 12, 96, 240, 4320, 20160, 241920, 1451520, 36288000, 159667200, 5748019200, 37362124800, 697426329600, 10461394944000, 334764638208000, 2134124568576000, 115242726703104000, 973160803270656000, 29194824098119680000, 510909421717094400000

Offset: 1

Author

Joseph L. Pe, Oct 04 2002

Keywords

• nonn
• easy

Examples

			There are four integers in {1, 2, ..., 3! = 6} that are coprime to 3, i.e. 1, 2, 4, 5. Hence a(3) = 4.
		

Crossrefs

Cf. A000010, A000142.

Programs

Mathematica

h[n_] := Module[{l}, l = {}; For[i = 1, i <= n!, i++, If[GCD[i, n] == 1, l = Append[l, i]]]; l]; Table[Length[h[i]], {i, 1, 9}]

Formula

a(n) = (n-1)!*phi(n). - Vladeta Jovovic, Dec 28 2002

Extensions

More terms from Michel ten Voorde Jun 20 2003