Generate 5 random digit and store same digit 8 times into array

  typedef struct digits
    {
      int *numbers; // 40 digit integer array malloc'd 
    } digits;

   // Section of function (not global)
   // Outer loop (loops 5 times)
   for (i = 5 - 1; i >=0; i--)
        {
            // loops 40 times
            for (j = 40 - 1; j >= 0; j--)

            { 
                // generates random number. I mod by 16 because I'm dealing 
                // with hexadecimals
                r -> numbers[j]  = rand () % 16;

                // If j is equal 5 store into array
                if (j == 5)
                {




                }

            }
        }

Question: I don't know how to complete this function to do what I want it to do. I have an idea of how it starts, and I've put in stuff into the loops, but it doesn't give me the expected output. I don't know how to do it to store the same 5 digits over and over until it's 40. Don't worry too much about the hex values, they display appropriately, they just don't repeat 8 times.

rand() generated: 3 8 9 5 10

Expected Output: 3895a3895a3895a3895a3895a3895a3895a3895a