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A285490
Lexicographically earliest sequence such that no two distinct, unordered pairs of distinct points ((n, a(n)), (m, a(m))) and ((k, a(k)), (j, a(j))) have the same midpoint.
3
1, 1, 1, 2, 1, 3, 5, 1, 7, 4, 9, 12, 1, 17, 21, 28, 6, 27, 2, 16, 14, 22, 41, 1, 50, 11, 33, 61, 9, 4, 73, 58, 88, 97, 40, 2, 26, 19, 95, 82, 45, 15, 1, 96, 54, 66, 125, 143, 57, 138, 10, 1, 171, 92, 184, 178, 191, 54, 110, 160, 13, 3, 202, 217, 122, 88, 42
OFFSET
1,4
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..4000 (first 650 terms from Peter Kagey)
EXAMPLE
a(1) = 1;
a(2) = 1;
a(3) = 1;
a(4) != 1 or else midpoint((1, 1), (4, 1)) = midpoint((2, 1), (3, 1));
a(4) = 2;
a(5) = 1;
a(6) != 1 or else midpoint((1, 1), (6, 1)) = midpoint((2, 1), (5, 1));
a(6) != 2 or else midpoint((3, 1), (6, 2)) = midpoint((4, 2), (5, 1));
a(6) = 3.
CROSSREFS
Cf. A285491 (pairs of not necessarily distinct points).
Sequence in context: A062705 A059234 A120852 * A058168 A367196 A058169
KEYWORD
nonn,look
AUTHOR
Peter Kagey, Apr 19 2017
STATUS
approved