I think about 51, I haven't been saving the best so far. I'll tee it to a file f...

scythe · on Dec 1, 2009

Try just placing 73 1's. You need to be able to place that many, but I can't get more than 65.

RiderOfGiraffes · on Dec 1, 2009

I've got 67 just using random placements with heuristics, programmed in Python. Apparently they've got 73 (which is 289/4 rounded up), and that's why they think this might be possible.

abentspoon · on Dec 1, 2009

I've placed 74 using an IP solver

      1 1 . . . . . 1 1 . . . . . 1 . .
      . 1 1 1 1 . . . . . . . . . . . .
      1 . 1 . . 1 . . . . . 1 . . . . 1
      1 . . 1 . . 1 . . . 1 . . . . 1 .
      1 . . . 1 . . . . 1 . . . 1 . . .
      . . . 1 . 1 . 1 . . . . . 1 . . .
      . 1 . . . 1 1 . . 1 . . . . . . .
      . . 1 . . . 1 1 . . . . 1 . . . .
      . . . . 1 1 . . 1 . . . 1 . . 1 .
      . . 1 . . . . . 1 1 1 . . . . . .
      . . . . 1 . . 1 . . 1 1 . . . . .
      . . . . . . 1 . 1 . . 1 . 1 . . .
      . . . 1 . . . . . 1 . 1 1 . 1 . .
      . 1 . . . . . . . . 1 . 1 1 . . 1
      . . 1 . . . . . . . . . . 1 1 1 .
      . . . . 1 . 1 . . . . . . . 1 . 1
      . . . . . . . 1 . 1 . . . . . 1 1

The solver chokes on anything larger than a 6x6 grid, but I've had good luck adding one row at a time to a smaller solution.

http://pastebin.com/m4c4696af

edit: He mentions that he already found a size 74 set in one of the linked pdfs. http://www.cs.umd.edu/~gasarch/BLOGPAPERS/17x17.pdf