Let Ni is a natural integer less than or equal to N, then exists the formula as follows: Ni ≤ N (1)
In terms of the above formula we can obtain the array as follows:
(1), (2), (3), (4), (5),.....,(N).
From the above arrangement we can obtain the formula as follows:
Ni(N) = N = Total of integers Ni less than or equal to N (2)
If Ni can be divided by the prime anyone less than or equal to ,√N , then sieves out the positive integer Ni; If Np can not be divided by all primes less than or equal to √N , then the number Np is a prime (Figure 1).