2. What is the 25th term of the sequence 3, 6, 11, 18, … ?

Answer 1

Look at the differences: 3,5,7,...
So the terms are
3, 3+3, 3+3+5, 3+3+5+7, ...
The sum 1+3+5+... = n^2
so, 3+3+5+7+... = n^2+2
The 25th term is 25^2 + 2 = 627

Answer 2

Hloniphile