A284486 The lexicographically earliest table read by antidiagonals such that any value appears at most twice on any straight line (of any slope).

1, 1, 1, 2, 1, 2, 2, 2, 3, 3, 3, 2, 3, 2, 4, 3, 4, 1, 1, 2, 3, 4, 3, 1, 3, 1, 4, 5, 4, 4, 2, 2, 3, 3, 5, 5, 5, 3, 5, 4, 2, 4, 6, 6, 7, 6, 5, 5, 6, 4, 7, 7, 4, 8, 2, 7, 5, 4, 5, 3, 6, 6, 7, 4, 8, 8, 6, 6, 8, 4, 7, 7, 8, 5, 5, 9, 3, 9, 8, 6, 6, 1, 8, 1, 9, 7, 3

Offset

1,4

Comments

Conjecture: Every value appears twice on every line of rational slope that contains an infinite number of points.

Links

Peter Kagey, Table of n, a(n) for n = 1..5000

Peter Kagey, Haskell program for enumerating sequence.

Example

Table begins:
    A   B   C   D   E   F
  +---+---+---+---+---+---+
1 | 1 | 1 | 2 | 3 | 4 | 3 |
  +---+---+---+---+---+---+
2 | 1 | 1 | 3 | 2 | 2 |   |
  +---+---+---+---+---+---+
3 | 2 | 2 | 3 | 1 |   |   |
  +---+---+---+---+---+---+
4 | 2 | 2 | 1 |   |   |   |
  +---+---+---+---+---+---+
5 | 3 | 4 |   |   |   |   |
  +---+---+---+---+---+---+
6 | 3 |   |   |   |   |   |
  +---+---+---+---+---+---+
a(17) = 4 (B5) because:
  1 already appears twice on the line connecting B1-B2,
  2 already appears twice on the line connecting B3-B4, and
  3 already appears twice on the line connecting D1-C3.

Crossrefs

Sequence in context: A207642 A053276 A064065 * A232194 A054705 A025800

Adjacent sequences: A284483 A284484 A284485 * A284487 A284488 A284489

Keyword

nonn,tabl,look

Author

Peter Kagey, Mar 27 2017

Status

approved