Roumanos primes

a = [2, 3, 5, 7, 11, 13, 17, 19]
for num in range(21, 101, 2):
        for y in a:
            if ((num%a[y]==0)==False and (num%num==0 and num%1==0)==True):
                a.append(num)
                print (num)
                y=0
        if len(a)==101:
            print (a[100])