Function to return the count of numbers from 1 to N which are not divisible by any number in the range [ 2 , 10 ]
int countNumbers ( int n ) { return n - n / 2 - n / 3 - n / 5 - n / 7 + n / 6 + n / 10 + n / 14 + n / 15 + n / 21 + n / 35 - n / 30 - n / 42 - n / 70 - n / 105 + n / 210 ; }