I just started to read "Friendly Introduction to Number Theory". Now I'm trying exercises 1-2
1.2. Try adding up the first few odd numbers and see if the numbers you get satisfy some sort of pattern. Once you find the pattern, express it as a formula. Give a geometric verification that your formula is correct.
I think the pattern is
Σ[n=0..n](2*n + 1)
But what is geometric verification? How should I answer this question?