In mathematics and theoretical computer science, the theory of computation encompasses the Sudan function, which is a function that is non-primitive recursive but still recursive. Similar to the Ackermann function, it was discovered and published by a Romanian mathematician called Gabriel Sudan in the 1920s. To find out more, take this short quiz.
Fx Fx Fx Fx
F(x * y) F(x*y)
A function of two negative integers x and y
A function of one positive integer x
A function of one negative integer y
A function of two positive integers x and y
F1 (x, y)
F2 (x, y)
Here's an interesting quiz for you.