Chükö

hexagonal numbers

A hexagonal number is a positive integer of the form n(2n - 1) for an integer n >= 1.

The first few hexagonal numbers are: 6, 15, 28, 45, 66, 91, 120, 153, 190, 231, 276, …

707 of the first one million positive integers are hexagonal.

Learn more about hexagonal numbers on wikipedia.

See other features.