How to make a scene load more random than others?

Here is a working code where a random scene is loaded via trigger etc between 2 and 5. However I want scene 4 to less likely appear than the others, I hope this is not too complicated, thanks in advance. I was thinking of (Random.Range(2,2,2,4,5,5,5,6,6,6)) something like that but I got errors.

Application.LoadLevel(Random.Range(2, 6));

Put your sequence in an array, use random.range to select value out of the array:

int[] levelNumbers = int[10] { 2,2,2,4,5,5,5,6,6,6 };

Application.LoadLevel(levelNumber[Random.Range(0, 9)]); // arrays are base 0.