Alternate Series of Fibonacci & Prime Numbers

FibPrime.py

'''
Series of Fibonacci and Prime numbers arranged alternatively
Fibo: 1,1,2,3,5...
Prime: 2,3,5,7,5...
Merged Series: 1, 2, 1, 3, 2, 5, 3, 7, 5, 11, 8, 13, 13, 17.........
'''
import math
def next_Fib(last, secLast):
    return last+secLast

def next_Prime(last):
    last=last+1
    while(True):
        if isPrime(last):
            return last
        else:
            last+=1

def isPrime(n):
    if(n <= 3): 
        return True
    if(n % 2 == 0 or n % 3 == 0): 
        return False
    i = 5
    while(i * i <= n) : 
        if (n % i == 0 or n % (i + 2) == 0) : 
            return False
        i = i + 6
    return True

IN = int(input("Enter the number of elements you want: "))
#IN = 14
series = [1,2,1]
for i in range(3,IN):
    if i%2==0:
        series.append(next_Fib(series[i-2], series[i-4]))
    else:
        series.append(next_Prime(series[i-2]))
print(*series)