Chain of primes X62405

You have to program the function has_prime_chain below. Remember that a non negative integer n is prime if and only if n is greater than one and the only divisors of n are one and n. The following auxiliar function may be helpful.

def is_prime(n):
    '''
    Requires a non negative integer n.
    Returns True when n is prime 
    Returns False when n is not prime
    '''
    if  n < 2:
        return False
    d = 2
    while d*d <= n:
        if n%d == 0:
            return False
        d += 1
    return True

• Write a function has_prime_chain(f, k) that given a list f of non negative integers and an integer k greater than zero returns the first valid index of f where a chain of primes of size k starts. If there is no such valid index it has to return −1. A chain of primes is a block of consecutive numbers in the list all of them being prime, delimited by non prime numbers or the ends of the list.

Scoring

The function counts 100 points.