Which nunber completes the sequence 1 1 3 2 4 6 5 25?

Answer 1

The rules are coming in a set of three:

Beginning with the ' 1 ' at the beginning,

then

1). square it

2). add 2

3). subtract 1

repeat

The 25 is the result of Rule #1.

So the sequence continues with 27, 26

Answer 2

27, 26, 676, 678, 677, 458329, ect... The pattern is multiply by itself, add two, subtract one (repeat)