A074818 Number of integers in {1, 2, ..., prime(n)} that are coprime to n.

2, 2, 4, 4, 9, 5, 15, 10, 16, 12, 29, 13, 38, 19, 26, 27, 56, 21, 64, 29, 42, 36, 80, 30, 78, 47, 69, 46, 106, 31, 123, 66, 84, 66, 103, 51, 153, 78, 104, 70, 175, 52, 187, 88, 106, 96, 207, 75, 195, 92, 147, 111, 237, 84, 187, 113, 170, 131, 273, 75, 279, 142, 176

Offset

1,1

Comments

Compare the definition of a(n) to phi(n) = number of integers in {1, 2, ..., n} that are coprime to n.

Links

Table of n, a(n) for n=1..63.

Example

There are five numbers in {1, 2, ..., prime(6) = 13} that are coprime to 6, i.e. 1, 5, 7, 11, 13. Hence a(6) = 5.

Mathematica

h[n_] := Module[{l}, l = {}; For[i = 1, i <= Prime[n], i++, If[GCD[i, n] == 1, l = Append[l, i]]]; l]; Table[Length[h[i]], {i, 1, 100}]

Crossrefs

Sequence in context: A287489 A288045 A292941 * A322112 A324409 A110199

Adjacent sequences: A074815 A074816 A074817 * A074819 A074820 A074821

Keyword

nonn

Author

Joseph L. Pe, Oct 04 2002

Status

approved