Implementation

import functools

@functools.cache
def fib(n):
    if n < 2:
        return n
    return fib(n - 1) + fib(n - 2)

There is no randomness on fundamental sciences like statics, physics, math etc. That sciences always searching for a reason. But we're need values which them looking like random in cryptography, tests, analysis, simulation etc. So, A pseudorandom sequence of numbers is one that appears to be statistically random, despite having been produced by a completely deterministic and repeatable process. In computer science we can describe it as a algorithm which is generating a Pseudo random values.