go =>
    foreach(M in 0..3)
        println([m=M,[a(M,N) : N in 0..16]])
    end,
    nl,
    printf("a2(4,1): %d\n", a2(4,1)),
    nl,
    time(check_larger(3,10000)),
    nl,
    time(check_larger(4,2)),
    nl.

% Using a2/2 and chop off large output
check_larger(M,N) =>
    printf("a2(%d,%d): ", M,N),
    A = a2(M,N).to_string,
    Len = A.len,
    if Len < 50 then
      println(A)
    else
      println(A[1..20] ++ ".." ++ A[Len-20..Len])
    end,
    println(digits=Len).

% Plain tabled (memoized) version with guards
table
a(0, N) = N+1 => true.
a(M, 0) = a(M-1,1), M > 0 => true.
a(M, N) = a(M-1,a(M, N-1)), M > 0, N > 0 => true.

% Faster and pure function version (no guards).
% (Based on Python example.)
table
a2(0,N) = N + 1.
a2(1,N) = N + 2.
a2(2,N) = 2*N + 3.
a2(3,N) = 8*(2**N - 1) + 5.
a2(M,N) = cond(N == 0,a2(M-1, 1), a2(M-1, a2(M, N-1))).