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.

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

Adjacent sequences: A285489 A285490 A285491 * A285493 A285494 A285495

Keyword

nonn,look

Author

Peter Kagey, Apr 19 2017

Status

approved