generators.ET0LTreeGrammar:
( { 1,2,3,4,5,6,7,8,9,10,11,12,13 },
  { F:3, -:0, sq:0 },
  {
    {
      1 -> F[2,3,4],
      2 -> F[2,5,6],
      3 -> F[7,3,4],
      4 -> F[8,9,-],
      5 -> F[7,5,10],
      6 -> F[8,11,12],
      7 -> F[7,5,6],
      8 -> F[8,9,-],
      9 -> F[-,-,-],
      10 -> F[8,11,13],
      11 -> F[-,13,13],
      12 -> F[-,13,12],
      13 -> F[-,13,13]
    },
    {
      1 -> sq,
      2 -> sq,
      3 -> sq,
      4 -> sq,
      5 -> sq,
      6 -> sq,
      7 -> sq,
      8 -> sq,
      9 -> sq,
      10 -> sq,
      11 -> sq,
      12 -> sq,
      13 -> sq
    }
  },
  1
)
