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 A049809 a(n)=number of Farey fractions of order n that are <=1/5; cf. A049805. 8
 1, 1, 1, 1, 2, 3, 4, 5, 6, 7, 9, 10, 12, 13, 15, 17, 20, 21, 24, 26, 29, 31, 35, 36, 40, 43, 47, 50, 55, 56, 62, 65, 69, 72, 77, 80, 87, 91, 96, 99, 107, 109, 117, 121, 126, 131, 140, 143, 151, 155, 162, 167, 177, 180, 188, 193, 201, 207 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 LINKS MATHEMATICA Farey[n_] := Union[Flatten[Join[{0}, Table[a/b, {b, n}, {a, b}]]]]; f[n_] := Length@ Select[ Farey@ n, # <= 1/5 &]; Array[f, 58] (* Robert G. Wilson v, Nov 14 2012 *) CROSSREFS Cf. A005728, A049806, A049807, A049808, A049810, A049811, A049812, A049813, A049814. Sequence in context: A048856 A067175 A225804 * A190278 A254636 A165763 Adjacent sequences:  A049806 A049807 A049808 * A049810 A049811 A049812 KEYWORD nonn AUTHOR STATUS approved

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Last modified September 27 08:39 EDT 2021. Contains 347689 sequences. (Running on oeis4.)