435 B
435 B
If you looked at the previous problems you probably know what comes now ... (Sieve of Eratosthenes)[http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes].
To lower the amount of A-B combinations we have to check here are 2 rules I found out:
B
must be a (positive) prime, otherwise n=0 wouldn't yield a prime number- When
B
is a primeA
must be uneven. Otherwise for n=0 the resulting number would be even and so not a prime.