Sudan function

Sudan function is a fast growing function discovered by. It is analogical with Ackermann function and formally defined as follows:

\(F_0(x,y) = x+y\)

\(F_{n+1}(x,0) = x\) (for \(n \geq 0\))

\(F_{n+1}(x,y+1) = F_n(F_{n+1}(x,y),F_{n+1}(x,y)+y+1)\) (for \(n \geq 0,y \geq 0\))

This function is less known than Ackermann one.