You can
put this solution on YOUR website!the next step (6th) in the table would be for 6 numbers, giving a sum of 6*7 or 42
if you think about the first 100 positive numbers; 1+100=101, 2+99=101, 3+98=101, etc.
there will be 50 such pairs ... so the sum is 101*50 or 5050