The left side is the sum of the arithmetic series: 1 + 3 + 5 + ... + 2n-1 The formula for this sum is where a1 = 1 and an = 2n-1 -------- Now we see if we can show that the right side is also equal to n2. The right side is the sum of an infinite geometric series The formula for this sum is where a1 = 1 and So the right side also equals n2. That proves they are equal. Edwin