CSHARP

sieve

internal class Program
{
  public static void Main()
  {
    var n = 53;
    var prime = SieveOfEratosthenes(n);
    for (int i = 2; i <= n; i++)
    {
      if(prime[i] == 0)
      {
        Console.WriteLine(i); ;
      }
    }

  }
  public static int[] SieveOfEratosthenes(int num)
  {
    var isPrime = new int[num + 1];
    for (int i = 2; i <= num; i++)
    {
      if (isPrime[i]==0)
      {
        for (int j = i * 2; j <= num; j += i)
        {
          // Eliminate multiples of i.   
          isPrime[j] = 1;
        }
      }
    }
    return isPrime;
  }
}