A285490 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

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

Adjacent sequences: A285487 A285488 A285489 * A285491 A285492 A285493

KEYWORD

nonn,look

AUTHOR

Peter Kagey, Apr 19 2017

STATUS

approved