k-nth x run length - collatz conjecture

#!/bin/python3
import os
import sys
import math
import random
import time


def check(n):

    count=0
    while True:
        count+=1
        if n%2==0:
            n=n/2
        else:
            n=(n*3)+1
        if n == 1:
            break
    return count

def get_d(x_val,k_val):
    safe=False
    if x_val%2==0:
        safe=True
    if safe==True:
        #print("safe==true")
        if k_val == 2:
            return 0
        elif k_val == 1:
            return 0
        else:
            d=0
            c=2
            for i in range(0, k_val-2):
                d+=c
                c=((c*2)*2)
            return d
    else:
        #print("safe==false")
        if k_val == 2:
            return 0
        elif k_val == 1:
            return 0
        elif k_val == 3:
            return 1
        else:
            d=1
            c=4
            for i in range(0, k_val-3):
                d+=c
                c=(c*2)*2
            return d

def get_nth(x_val, k_val):
    v=int(pow(2, x_val))
    if k_val == 1:
        return v
    d=get_d(x_val,k_val)
    v = math.floor(((v-2)/2)/3)
    v = v - d
    return v

def get_k(x_val):
    return math.ceil(x_val/2)-1



def run():
    x_value=int(input("Enter sequence termination length (e.g: 5):: "))
    k=get_k(x_value)
    k_value=int(input("Enter nth number from 1 - "+str(k)+":: "))
    if k_value < 1 or k_value > k:
        return False
    n=get_nth(x_value, k_value)
    check_n=check(n)

    print("Termination Length: "+str(x_value))
    print("k-nth-set-size: "+str(k))
    #print("kv: "+str(k_value))
    print("k-nth("+str(k_value)+") == "+str(n))
    if check_n == x_value:
        print("Termination get_nth("+str(x_value)+", "+str(k_value)+") == check_n("+str(n)+") == "+str(check_n))
        print("PASSED TEST")
    else:
        print("FAILED TEST")
    return True

def start():
    ran=run()
    if ran==False:
        start()

start()