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%I #13 Mar 30 2017 06:19:48
%S 1,1,1,2,1,2,2,2,3,3,3,2,3,2,4,3,4,1,1,2,3,4,3,1,3,1,4,5,4,4,2,2,3,3,
%T 5,5,5,3,5,4,2,4,6,6,7,6,5,5,6,4,7,7,4,8,2,7,5,4,5,3,6,6,7,4,8,8,6,6,
%U 8,4,7,7,8,5,5,9,3,9,8,6,6,1,8,1,9,7,3
%N The lexicographically earliest table read by antidiagonals such that any value appears at most twice on any straight line (of any slope).
%C Conjecture: Every value appears twice on every line of rational slope that contains an infinite number of points.
%H Peter Kagey, <a href="/A284486/b284486.txt">Table of n, a(n) for n = 1..5000</a>
%H Peter Kagey, <a href="/A284486/a284486.hs.txt">Haskell program for enumerating sequence</a>.
%e Table begins:
%e A B C D E F
%e +---+---+---+---+---+---+
%e 1 | 1 | 1 | 2 | 3 | 4 | 3 |
%e +---+---+---+---+---+---+
%e 2 | 1 | 1 | 3 | 2 | 2 | |
%e +---+---+---+---+---+---+
%e 3 | 2 | 2 | 3 | 1 | | |
%e +---+---+---+---+---+---+
%e 4 | 2 | 2 | 1 | | | |
%e +---+---+---+---+---+---+
%e 5 | 3 | 4 | | | | |
%e +---+---+---+---+---+---+
%e 6 | 3 | | | | | |
%e +---+---+---+---+---+---+
%e a(17) = 4 (B5) because:
%e 1 already appears twice on the line connecting B1-B2,
%e 2 already appears twice on the line connecting B3-B4, and
%e 3 already appears twice on the line connecting D1-C3.
%K nonn,tabl,look
%O 1,4
%A _Peter Kagey_, Mar 27 2017
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