Stores the product of every pair of prime number
List < int > prod = new List < int > ( ) ; SieveOfEratosthenes ( ) ; int l = primes . Count ; for ( int i = 0 ; i < l ; i ++ ) { for ( int j = i + 1 ; j < l ; j ++ ) { if ( primes [ i ] * primes [ j ] > 0 ) prod . Add ( primes [ i ] * primes [ j ] ) ; } }