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.

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

Author

Peter Kagey, Apr 19 2017

Keywords

• nonn
• look

Examples

			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.
		

Links

• Giovanni Resta, Table of n, a(n) for n = 1..4000 (first 650 terms from Peter Kagey)

Crossrefs

Cf. A285491 (pairs of not necessarily distinct points).