# Bertrand's Postulate in C++

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Bertrand’s postulates is a mathematical showroom which states that for every number n>3, there exists a prime number p which lies between n and 2n-2.

## The formula for Bertrand's Postulate

n < p < 2n -2

Where n is a number such that n>3 and p is a prime number.

Prime number − A number is a prime number if it's only factors are 1 and itself.

A less restrictive formulation of Bertrand’s postulate is

n < p < 2n , for all n>1.

## Examples

### Number

5

### Output

7

### Explanation

prime number in range 5 and 2*5 i.e. prime number between 5 and 10

### Number

11

### Output

13, 17, 19

### Explanation

prime number in range 11 and 2*11 i.e. prime number between 11 and 22

## Program to find prime number using Bertrand’s postulates

//Program to find prime number using Bertrand’s postulates −

## Example

Live Demo

#include <iostream>
using namespace std;
void printPrime(int n) {
int flag = 0;
for (int i = 2; i * i <= n; i++)
if (n % i == 0) // i is a factor of n
flag++;
if(flag == 0)
cout<<n<<" ";
}
int main() {
int n = 22;
cout<<"Prime numbers in range ("<<n<<", "<<2*n<<") :\t";
for (int p = n + 1; p < 2 * n - 2; p++)
printPrime(p);
return 0;
}

## Output

Prime numbers in range (22, 44) : 23 29 31 37 41
Updated on 17-Jul-2020 12:00:29