centered hexagonal number
nounUK /ˈsɛntəd hɛkˈsæɡənəl ˈnʌmbə/
US /ˈsɛntərd hɛkˈsæɡənəl ˈnʌmbər/
A centered hexagonal number is a number of dots that can make a hexagon shape with one dot in the middle.
The first few centered hexagonal numbers are 1, 7, 19, and 37.
OTHER MEANINGS
2. A figurate number that counts the points in a hexagonal lattice arranged in concentric rings around a central point.
Mathematicians study centered hexagonal numbers in number theory and combinatorics.
3. A sequence of integers given by the formula 3n(n−1)+1, where n is a positive integer.
Plugging n = 3 into 3n(n−1)+1 gives 19, a centered hexagonal number.
4. A number that can be represented by a hexagonal pattern of dots with a single dot at the center.
The centered hexagonal number 7 looks like a flower with one dot surrounded by six.