This is one of my earliest color optical illusions. There is no yellow or green in the diamond shapes, just vertical black lines! (If you don’t believe it, use a eyedropper tool to check it.)

## Perfect “Square” Circle

Numbers 1 to 32 are placed along the circumference of a circle without repeating any number and still the sum of any two adjacent numbers in this circle is a perfect square!

## Visual Proof (sum of cubes)

The sum of the sequence of the first *n* cubes equals [*n*(*n*+1)/2]² as shown below:

1³+2³+3³+…+*n*³ = (1+2+3+…+*n*)² = [*n*(*n*+1)/2]²