# Which number is the odd one out?

Which one of the numbers below is the odd one out and why?

1, 2, 3, 4, 5, 8, 13

Hint:

Look at the first tag.

• I've noticed that I'm getting some downvotes so could anyone tell me what's wrong with my post? Thanks! Sep 11, 2018 at 6:25
• Welcome to Puzzling. I assume the downvotes are because your "puzzle" is not that challenging. You got 2 (correct) answers in the first 2 minutes after you posted it. but don't discourage. I happened to a lot of new people in here (me included). I agree that the lack of explanations may be frustrating (that's why I tried to explain this). Look on the bright side. Take this as constructive criticism (even if it doesn't look like it) and come back with more challenging puzzles. Sep 11, 2018 at 7:30

4
Because this is the Fibonacci sequence and 4 is not in it.

Then the number $x_n$ is formed by $x_{n-1} + x_{n-2}$
• I was gonna say, I think I saw a similar sequence in an IQ test... and a particular kind of sequence occurs in IQ tests quite often... $(+1)$ :P Sep 11, 2018 at 11:33