hexagonal number
nounUK /hɛkˈsæɡənəl ˈnʌmbə/
US /hɛkˈsæɡənəl ˈnʌmbər/
A hexagonal number is a number of dots that can be arranged in a shape like a honeycomb hexagon.
The first few hexagonal numbers are 1, 6, 15, and 28.
OTHER MEANINGS
2. A number that counts the dots in a pattern of nested hexagons.
Teachers used hexagonal numbers to show how patterns grow.
3. A term in recreational mathematics for numbers of the form n(2n−1).
The formula n(2n−1) gives the nth hexagonal number.
4. A number that can be shown as a hexagon made of evenly spaced points.
She drew 15 dots as a hexagonal number on the board.