A126707 a(n) = number of composites coprime to n and <= the n-th composite.

1, 0, 2, 1, 4, 0, 6, 2, 5, 1, 11, 0, 13, 2, 5, 4, 17, 1, 19, 3, 9, 5, 23, 2, 19, 7, 15, 6, 29, 0, 31, 9, 16, 10, 21, 3, 37, 12, 20, 8, 41, 2, 43, 12, 18, 15, 47, 5, 41, 10, 26, 14, 53, 5, 36, 13, 30, 19, 59, 2, 61, 20, 28, 21, 44, 6, 67, 21, 37, 10, 71, 9, 73, 25, 29, 23, 56, 7, 79, 16, 45

Offset

1,3

Links

Table of n, a(n) for n=1..81.

Mathematica

c = Select[Range[120], # != 1 && ! PrimeQ[ # ] &]; Table[Length[Select[Take[c, n], GCD[ #, n] == 1 &]], {n, Length[c]}] (* Ray Chandler, Feb 17 2007 *)

Crossrefs

Cf. A002808.

Sequence in context: A033883 A106316 A300721 * A326305 A057458 A291193

Adjacent sequences: A126704 A126705 A126706 * A126708 A126709 A126710

Keyword

nonn

Author

Leroy Quet, Feb 11 2007

Extensions

Extended by Ray Chandler, Feb 17 2007

Status

approved