if we take a example

2,5,9...from 2 to 5 there is difference of 3 numbers from 5 to 9 there is difference of 4 numbers like this we have to answer the question

from 3 to 5 there is difference of 2 numbers from 5 to 8 there is difference of 3 numbers from 8 to 12 there is difference of 4 numbers and from 12 to 17 there is difference of 5 numbers like this we have to write the next number we have to add 6 to 17 numbers

the answer is 23