A049807 a(n)=number of Farey fractions of order n that are <=1/3; cf. A049805.

1, 1, 2, 3, 4, 5, 7, 8, 10, 12, 15, 16, 20, 22, 25, 28, 33, 35, 41, 43, 47, 51, 58, 61, 68, 72, 78, 82, 91, 93, 103, 108, 115, 121, 129, 133, 145, 151, 159, 165, 178, 182, 196, 202, 210, 218, 233, 238, 252, 258, 269, 277, 294, 300

Offset

1,3

Links

Table of n, a(n) for n=1..54.

Mathematica

Farey[n_] := Union[Flatten[Join[{0}, Table[a/b, {b, n}, {a, b}]]]]; f[n_] := Length@ Select[ Farey@ n, # <= 1/3 &]; Array[f, 54] (* Robert G. Wilson v, Nov 14 2012 *)

Crossrefs

Cf. A005728, A049806, A049808, A049809, A049810, A049811, A049812, A049813, A049814.

Sequence in context: A008754 A029005 A132154 * A008753 A029004 A332728

Adjacent sequences: A049804 A049805 A049806 * A049808 A049809 A049810

Keyword

nonn

Author

Clark Kimberling

Status

approved