ack = (m, n):
  if (m == 0): n + 1
. elsif (n == 0): ack(m - 1, 1)
. else: ack(m - 1, ack(m, n - 1)).
.

4 times(m):
  7 times(n):
    ack(m, n) print
    " " print.
  "\n" print.