Sequences

Let $\{a_1,a_2,a_3,a_4,a_5\ldots a_n\}$ be a sequence such that $a_1=2$ and $a_n-a_{n-1}=2n$ for all $n>1$ .

Then let $Z=a_1+a_2+a_3+\ldots a_{20}$ .

What is the sum of digits of $Z$ ?

Note :

• For no confusion, the sum of the digits in 99929 is 38. The sum of the digits in 1000 is 1.