A049808 a(n)=number of Farey fractions of order n that are <=1/4; cf. A049805.

1, 1, 1, 2, 3, 4, 5, 6, 8, 9, 11, 12, 15, 17, 19, 21, 25, 26, 30, 32, 36, 39, 44, 46, 51, 54, 58, 61, 68, 70, 77, 81, 87, 91, 97, 100, 109, 114, 120, 124, 134, 136, 146, 151, 157, 163, 174, 178, 189, 194, 202, 208, 221, 226, 236, 242

Offset

1,4

Links

Table of n, a(n) for n=1..56.

Mathematica

Farey[n_] := Union[Flatten[Join[{0}, Table[a/b, {b, n}, {a, b}]]]]; f[n_] := Length@ Select[ Farey@ n, # <= 1/4 &]; Array[f, 56] (* Robert G. Wilson v, Nov 14 2012 *)

Crossrefs

Cf. A005728, A049806, A049807, A049809, A049810, A049811, A049812, A049813, A049814.

Sequence in context: A295796 A030789 A030749 * A344933 A191886 A184115

Adjacent sequences: A049805 A049806 A049807 * A049809 A049810 A049811

Keyword

nonn

Author

Clark Kimberling

Status

approved