I want to give a group of friends a riddle I heard to solve but the only problem is... I don't know the answer! Here is the riddle:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

There is an error in this list of numbers above and it may seem impossible to find but it's there. I don't know what it is, can you help me?

I've seen that one, too.. And I couldn't figure out what the answer was, because all the numbers are there, in the right order...

0 is missing, that's my guess

That's stupid, 0 isn't really a number.

Of course 0 is a real number, but I agree it is a silly guess

I can't figure it out! It's eating me away!!

I can't figure it out! It's eating me away!!!

The answer was already given.

Is that the entire riddle, did they just write the numbers or were there words as well? If there were words, than what are they?

No words. I guess it's no 0! Oh well!

I don't think so like I said my guess was stupid

No 0...

Or...

Why does it stop at 20?