This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A317988 #22 Jan 09 2022 23:36:25
%S A317988 0,1,1,1,1,2,1,3,2,3,1,4,3,4,1,5,2,5,3,5,4,5,1,6,5,6,1,7,2,7,3,7,4,7,
%T A317988 5,7,6,7,1,8,3,8,5,8,7,8,1,9,2,9,4,9,5,9,7,9,8,9,1,10,3,10,7,10,9,10,
%U A317988 1,11,2,11,3,11,4,11,5,11,6,11,7,11,8,11,9,11,10,11,1,12,5,12,7,12,11,12
%N A317988 Farey fraction tree, reading each fraction's numerator first, then its denominator.
%C A317988 0 < a(2n-1)/a(2n) < 1 for n > 2.
%C A317988 This appears to be A038568 preceded by 0,1,1. - _Peter Kagey_, Jan 09 2022
%F A317988 0,1 followed by the interleaving of A038566 & A038567.
%e A317988 Farey fraction tree begins:
%e A317988 0/1 1/1
%e A317988 1/2
%e A317988 1/3 2/3
%e A317988 1/4 3/4
%e A317988 1/5 2/5 3/5 4/5
%e A317988 1/6 5/6
%e A317988 1/7 2/7 3/7 4/7 5/7 6/7
%e A317988 1/8 3/8 5/8 7/8
%e A317988 1/9 2/9 4/9 5/9 7/9 8/9
%e A317988 1/10 3/10 7/10 9/10
%e A317988 ...
%t A317988 Table[ If[ GCD[n, d] == 1, {n, d}, {}], {d, 0, 12}, {n, 0, d}] // Flatten
%Y A317988 Cf. A038566, A038567, A038568.
%K A317988 nonn
%O A317988 1,6
%A A317988 _Robert G. Wilson v_, Oct 03 2018