where are you getting stuck with these?
probably need to be positive integers >0.
Are any of the numbers allowed to be zero?
If they are allowed to be negative or non-integers, that leaves infinitely
-14+1+2, -15+1+3 etc
Hence, start with 1, add 2 and find out what is.
Then start again at 1, add 3 and find out what is.
When finished with 1, go on to 2 and make sure you leave out all numbers
less than 2.
Then go on to 3, leaving out all numbers less than 3.
Continue until done, there are only a few.