

A277433


Martin Gardner's minimal no3inaline problem, all slopes version.


3




OFFSET

1,2


COMMENTS

a(n) is the minimal number of counters that can be placed on an n X n grid, no three in a straight line, such that adding one more counter on any vacant grid point will produce three in a line. Lines can have any slope.
The "queens" version of this problem, where lines are restricted to vertical, horizontal and diagonal, is A219760.
a(11) <= 10, a(12) <= 10.


LINKS

Table of n, a(n) for n=1..10.
Robert Israel, Examples for n <= 12 (provably optimal for n <= 10).


CROSSREFS

Cf. A219760.
Sequence in context: A073229 A116446 A102126 * A219760 A097918 A256416
Adjacent sequences: A277430 A277431 A277432 * A277434 A277435 A277436


KEYWORD

nonn,more


AUTHOR

Robert Israel, Oct 14 2016


STATUS

approved



