Hello everybody (Long time no see),
is there a formula that allows us to count the multiples of prime numbers up to a number .
What i mean:
For example we have three primes . How many multiples (of these three numbers) are up to number
By sequentian steps we have that:
->There are 15 multiples of 2
->There are 10 multiples of 3. However numbers $6, 12, 18, 24, 30$ have been already counted as multiples of 2. So eventually there are 5 multipes of 3, that are not already counted.
->There are only 2 (new) multiples of 5 (5, 25)
So total we have 15 (multiples of 2) + 5 (new multiples of 3) + 2 (new multiples of 5) = 22
So, is there a quick formula for counting the multiples (once)?
Thanks all for your time and you response