Answer :

In all the cases, the number is multiplied by itself and added 1 to it. so the answer is 26
yoboiajeccles

Answer: 26

There is a pattern. It is squared then added with one.

For visual reference-

2=5 (2*2=4, 4+1=5)

3=10 (3*3=9, 9+1=10)

4=17 (4*4=16, 16+1=17)

5=?? (do the same thing)

so

5=26 (5*5=25, 25+1=26)