And that double-counts board layouts that are symmetric. Digging through the references led me to this page[1] which has a nice discussion on different ways to

And that double-counts board layouts that are symmetric. Digging through the references led me to this page[1] which has a nice discussion on different ways to compute the number of states. Without symmetry you have 5478 possible board states, which is less than the 6120 you would get by adding rotation/flip bits to the 765 states. Both require 13 bits though. Too bad, I was hoping it would fit into a 12-bit PDP-8 word :) [1]https://web.archive.org/web/20020513063952/http://www.mathrec.org/old/2002jan/solutions.html https://web.archive.org/web/20020513063952/http://www.mathre...