This is the concept of sequences and series, we are required to get the next number in the series;
3,4,8,17,33,...
To get the next number we proceed as follows;
4-3=1=1^2
8-4=4=2^2
17-8=9=3^2
33-17=16=4^2
From the above difference, we notice that the difference between the consecutive number is the square of the digits from 1. Therefore our next number will be:
33+5^2
=33+25
=60
Our next number is 60