Are you talking about POSITIVE ODD and EVEN INTEGERS less than 50?
If so, then POSITIVE ODD INTEGERS less than 50 would begin at 1 and end at 49, in which case you will have 25 numbers.
If you're talking about POSITIVE EVEN INTEGERS less than 50, that series begins at 0 (zero) and ends at 48, in which case you will also have 25 numbers.