OFFSET
1,2
MATHEMATICA
Farey[n_] := Union[Flatten[Join[{0}, Table[a/b, {b, n}, {a, b}]]]]; f[n_] := Length@ Select[ Farey@ n, # <= 1/2 &]; Array[f, 53] (* Robert G. Wilson v, Nov 14 2012 *)
a[n_] := Count[FareySequence[n], f_ /; f <= 1/2]; Array[a, 53] (* Jean-François Alcover, Sep 25 2018 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved