There are couple of ways this can be done.
First, is converting to list and then to array again:
List<int> tmpList = intArry.ToList();tmpList.Add(anyInt);intArry = tmpList.ToArray();
Now this is not recommended as you convert to list and back again to array. If you do not want to use a list, you can use the second way which is assigning values directly into the array:
int[] terms = new int[400];for (int runs = 0; runs < 400; runs++){ terms[runs] = value;}
This is the direct approach and if you do not want to tangle with lists and conversions, this is recommended for you.