Question

The, sum of the first 20 terms of the sequence 1, 4, 9, $\dots$ is

Answer 1

The given series is of the form, $1^2,2^2,3^2,4^2.....$

The formula to find sum of first $n$ terms of a sequence of squares of natural numbers $=\frac{n(n+1)(2n+1)}{6}$

So, sum of first $20$ terms of the given sequence $=\frac{20(20+1)\left(2\right(20)+1)}{6}=2870$