I've placed 74 using an IP solver 1 1 . . . . . 1 1 . . . . . 1 . . . 1 1 1 1 . . . . . . . . . . . . 1 . 1 . . 1 . . . . . 1 . . . . 1

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 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 http://www.cs.umd.edu/~gasarch/BLOGPAPERS/17x17.pdf