Had difficulties implementing intro to Coroutines from unitypatterns.com. Help?

I can't figure out the cause of the problem. I've tried restarting Unity and rebooting my PC. I've tried passing string and method names. Switching 0 to null made no difference. Nothing ever changes. I'm always consistently getting either 1 Hello when yield comes before Debug.Log, and 2 Hellos when yield comes after. Any ideas??? I literally only put this online to ask this question here. I really think I need to have Coroutines work properly, I don't know what the source of the problem is.

Gist with syntax highlighting: https://gist.github.com/nastajus/e420713c2aa3be04b8cb

Github entire but simple project: https://github.com/nastajus/CoroutinesLearning

Unity Patterns tutorial: http://unitypatterns.com/introduction-to-coroutines/

The most interesting result was when I append i to the output it prints 5 times instead. Very weird and confusing based off the tutorial.

     void Start(){
         StartCoroutine("SayHello5Times");    //doesn't work right
     }

     IEnumerator SayHello5Times(){
         for (int i = 0; i < 5; i++){
  
             //instructions: comment out other block
  
             yield return 0;
             Debug.Log("Hello");            //prints once
             //Debug.Log("Hello " + i);    //prints 5 times
         }
     }