cp's OEIS Frontend

A157807 Numerators of fractions arranged in "antidiagonal boustrophedon" ordering with equivalent fractions removed: (1/1, 2/1, 1/2, 1/3, 3/1, 4/1, 3/2, 2/3, 1/4, 1/5, 5/1, 6/1, 5/2, ...).

%I A157807 #28 Oct 10 2023 14:02:19
%S A157807 1,2,1,1,3,4,3,2,1,1,5,6,5,4,3,2,1,1,3,5,7,8,7,5,4,2,1,1,3,7,9,10,9,8,
%T A157807 7,6,5,4,3,2,1,1,5,7,11,12,11,10,9,8,7,6,5,4,3,2,1,1,3,5,9,11,13,14,
%U A157807 13,11,8,7,4,2,1,1,3,5,7,9,11,13,15,16,15,14
%N A157807 Numerators of fractions arranged in "antidiagonal boustrophedon" ordering with equivalent fractions removed: (1/1, 2/1, 1/2, 1/3, 3/1, 4/1, 3/2, 2/3, 1/4, 1/5, 5/1, 6/1, 5/2, ...).
%H A157807 Robert Israel, <a href="/A157807/b157807.txt">Table of n, a(n) for n = 1..10000</a>
%p A157807 R:= NULL: count:= 0:
%p A157807 for m from 2 while count < 100 do
%p A157807   S:= select(t -> igcd(t,m-t)=1, [$1..m-1]);
%p A157807   count:= count+nops(S);
%p A157807   if m::even then R:= R, op(S) else R:= R, seq(m-t,t=S) fi;
%p A157807 od:
%p A157807 R; # _Robert Israel_, Oct 09 2023
%o A157807 (Python)
%o A157807 from math import gcd
%o A157807 for s in range(2, 100, 2):
%o A157807   for i in range(1, s):
%o A157807     if gcd(i, s - i) != 1: continue
%o A157807     print(i)
%o A157807   for i in range(s, 0, -1):
%o A157807     if gcd(i, s + 1 - i) != 1: continue
%o A157807     print(i)
%o A157807 # _Hiroaki Yamanouchi_, Oct 06 2014
%Y A157807 Cf. A157813 (denominators), A038566.
%Y A157807 With Cantor's ordering: A020652, A020653, A352911.
%K A157807 nonn,frac
%O A157807 1,2
%A A157807 _Ron R. King_, Mar 07 2009
%E A157807 A-number in cross-reference corrected by _R. J. Mathar_, Sep 23 2009
%E A157807 a(19)-a(20) corrected and a(58)-a(82) added by _Hiroaki Yamanouchi_, Oct 06 2014
%E A157807 Name corrected by _Andrey Zabolotskiy_, Oct 10 2023