Sieve of Eratosthenes to find new numbers

Why is Math so hard for some children? We want to start from the vision and the teorethical dissertation, supported by educational and philosophical theories that here are presented, to use the concept of reification. A new element in contemporary reason is therefore the re-emergence of the subject, the reconsideration of the distinction between objective and subjective, between that which belongs to the subject and that which belongs to the object. We want to submit an experience of study with 10-year old children, at primary school. The aim is to help children in forming the abstract concept of prime numbers and to use this concept for build other concepts.