program mertens;
    m := [1] * 1000;
    loop for n in [1..#m] do
        m(n) -:= 0 +/[m(n div k) : k in [2..n]];
    end loop;

    print("The first 99 Mertens numbers:");
    putchar("   ");
    loop for n in [1..99] do
        putchar(lpad(str m(n), 3));
        if n mod 10=9 then print; end if;
    end loop;

    zero := #[n : n in [1..#m] | m(n) = 0];
    cross := #[n : n in [1..#m] | m(n) = 0 and m(n-1) /= 0];

    print("M(N) is zero " + str zero + " times.");
    print("M(N) crosses zero " + str cross + " times.");
end program;