Essentially we have

two waysto solve this problem:

**A**–**Testing**in order**one by one**if the number**is prime or not**. And if it is write it.

**B**–**Store**all numbers and**discard**the multiples of primes we know. (**Sieve of Eratosthenes**).

**WHAT IS MORE CONVENIENT?**

- Choice A

**Disadvantages**: We have to calculate if the number is prime or not for **each number**.**Advantages**: We don’t need **store** the numbers.

- Choice B

**Disadvantages**: We need **store** all numbers (although We can drastically reduce)**Advantages**: It’s **more faster** because the primes are not calculated.

We Choose **option B** because it is much easier **store** than process and also can greatly **reduce** the numbers we store considering that we can eliminate **half** of the numbers if we eliminate the **even** numbers in the list, and a **third** if we eliminate **multiples of 3** and so on, while we can keep indexing properly.