Loop to find the number of ordered pairs for every combination of the prime numbers
for ( int p = 1 ; p < size ; p ++ ) { for ( int q = 1 ; q < size ; q ++ ) { if ( prime [ p ] == 0 && prime [ q ] == 0 && a * p + b * q < size ) { freq [ a * p + b * q ] ++ ; } } } }