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

1,3

Links

Table of n, a(n) for n=1..22.

Formula

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

Example

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

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}]

Crossrefs

Cf. A000010, A000142.

Sequence in context: A197919 A358003 A009651 * A287596 A364901 A268363

Adjacent sequences: A074927 A074928 A074929 * A074931 A074932 A074933

Keyword

nonn,easy

Author

Joseph L. Pe, Oct 04 2002

Extensions

More terms from Michel ten Voorde Jun 20 2003

Status

approved