Calculate the Collatz series -- see https://youtu.be/5mFpVDpKX70

collatz.py

#!/usr/bin/env python3

def collatz(n: int, p = True):
    i: int = 0

    while n > 1:
        if n % 2 != 0:
            n = 3*n +1
            i += 1
            if p: print(f"{i}: {n}")
        n //= 2
        i += 1
        if p: print(f"{i}: {n}")

    return(i)


if __name__ == "__main__":
    import argparse
    parser = argparse.ArgumentParser()
    parser.add_argument("n", help="run the 3n+1 function on n", type=int)
    parser.add_argument("-p", "--print", help="print all the intermediate steps", action="store_true")
    args = parser.parse_args()

    print(f"{collatz(args.n, args.print)} steps for collatz({args.n:,})")