Find the pattern:

1,1,2,3,5,8 ...

It's the 1 because the other numbers don't have a another to go with it

The pattern is simply the two previous numbers added together.

We start with 1.

The next number is that 1 added to a blank before it to equal 1.

The third number comes after two 1s. Add them together to get 2.

The fourth number comes after a 2 and a 1. Add them together to get 3.

Therefore the next number in the pattern would be 13.