### Series Sums

Let S1 = 1 , S2 = 2 + 3, S3 = 4 + 5 + 6 ,........ Calculate S17.

### Sums of Powers - A Festive Story

A story for students about adding powers of integers - with a festive twist.

### Cellular

Cellular is an animation that helps you make geometric sequences composed of square cells.

# Natural Sum

##### Stage: 4 Challenge Level:

The picture illustrates the sum $1 + 2 + 3 + 4 = (4 \times5)/2$. Prove the general formula for the sum of the first $n$ natural numbers and the formula for the sum of the cubes of the first n natural numbers. See the problem Picture Story .