Ackermann Function

[bplus]

The Ackermann function, but the program crashes as soon as one enter "ackermann(4, 1)". Why? 

The result of (4, 1) is 65533, which is in range. The program crashes, both in QB64 and in C (GCC - WinGW 11.02). 

Because the Integer Range is +- 32K and change. Try _Unsigned Long or _Unsigned _Integer64 IF the numbers and calculations with them are Always Positive (no big variable subtractions) that will get you the greatest upper limit.

Of what use are the Ackermann numbers?