# 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! – ThyrsoidMouse73 Sep 11 '18 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. – Marius Sep 11 '18 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 – Mr Pie Sep 11 '18 at 11:33