My previous writeup of the L18 result at

https://web.archive.org/web/20150310085851/http://tromp.gith...

answers your question: "only L2, L3, L7 and L10 can be represented as legal positions themselves", graced with a picture of L10. L2=57 is 2010 in ternary, which looks like

    O .
    X .