In fact, although there is a pattern, the line starting with 0 is deleted to avoid -ve nos. So, the general pattern would have been,
0 -1 -2 -3 -4 1 2 3 4 5 10 9 8 7 6 11 12 13 14 15 20 19 18 17 16 21 22 23 24 25
So, you start with 0, increment your variable i by 10 in each iteration, and print lines starting with i and i + 1, except when loop variable is 0. I think you can figure out how to do the individual lines and translate this into code.