Main function calling WriteFactorial in sync

AsyncAwait_Main_Sync

public void Main()
{
    for (int counter = 1; counter < 5; counter++)
    {
        if (counter % 3 == 0)
        {
            WriteFactorial(counter);
        }
        else
        {
            Console.WriteLine(counter);
        }
    }
    Console.ReadLine();
}