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A285492
a(n) is the least positive integer not already appearing 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.
2
1, 2, 3, 5, 4, 8, 11, 6, 15, 12, 9, 7, 20, 25, 16, 30, 36, 10, 18, 47, 27, 38, 59, 13, 58, 73, 43, 81, 19, 26, 96, 14, 45, 109, 121, 72, 54, 44, 70, 17, 98, 137, 60, 156, 29, 113, 155, 92, 22, 145, 173, 63, 112, 46, 39, 136, 204, 24, 219, 174, 21, 237, 253, 80
OFFSET
1,2
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..3000 (first 650 terms from Peter Kagey)
EXAMPLE
a(4) != 4 or else midpoint((4,4), (1,1)) = midpoint((2,2), (3,3)), thus
a(4) = 5.
a(6) != 6 or else midpoint((6,6), (3,3)) = midpoint((4,5), (5,4));
a(6) != 7 or else midpoint((6,7), (1,1)) = midpoint((3,3), (4,5)); thus
a(6) = 8.
CROSSREFS
Cf. A285490.
Sequence in context: A046708 A338251 A185728 * A272090 A120255 A245608
KEYWORD
nonn,look
AUTHOR
Peter Kagey, Apr 19 2017
STATUS
approved