But it was triangular numbers that got the ball rolling in the first place. Sign up here for the weekly Science Times newsletter.

How Much of Our Math Series Did You Retain? Try This Quiz. Test your knowledge of taxicab geometry, triangular numbers, the golden ratio and more.

Each day brings a greater triangular number of gifts. But how can we compute the total number without actually adding them up? We need to sum the first 12 triangular numbers.