to m :n
  if 0 = :n [output 0]
  output :n - f m :n-1
end
to f :n
  if 0 = :n [output 1]
  output :n - m f :n-1
end

show cascade 20 [lput m #-1 ?] []
[1 1 2 2 3 3 4 5 5 6 6 7 8 8 9 9 10 11 11 12]
show cascade 20 [lput f #-1 ?] []
[0 0 1 2 2 3 4 4 5 6 6 7 7 8 9 9 10 11 11 12]