In this pattern you can notice that the numbers and letters alternate, 1 by 1. Also, from each number to the next, 3 is added. (4 + 3 = 7, 7 + 3 =10, 10 + 3 = 13). For the letters, it goes in alphabetical order with two letters being skipped between each letter. (D, G, J).
Based on the number letter pattern, the last value is a number indicating a letter is next. Now, we just follow the same "skip two" letters pattern to get from J to M.
