polygonal number
11Triangular number — The first six triangular numbers A triangular number or triangle number numbers the objects that can form an equilateral triangle, as in the diagram on the right. The nth triangle number is the number of dots in a triangle with n dots on a side;… …
12Dodecagonal number — A dodecagonal number is a figurate number that represents a dodecagon. The dodecagonal number for n is given by the formula 5n2 4n, with n > 0. The first few dodecagonal numbers are: 1, 12, 33, 64, 105, 156, 217, 288, 369, 460, 561, 672, 793,… …
13Centered pentagonal number — A centered pentagonal number is a centered figurate number that represents a pentagon with a dot in the center and all other dots surrounding the center in successive pentagonal layers. The centered pentagonal number for n is given by the formula …
14List of recreational number theory topics — This is a list of recreational number theory topics (see number theory, recreational mathematics). Listing here is not pejorative: many famous topics in number theory have origins in challenging problems posed purely for their own sake. See list… …
15Square number — In mathematics, a square number, sometimes also called a perfect square, is an integer that can be written as the square of some other integer; in other words, it is the product of some integer with itself. So, for example, 9 is a square number,… …
1622 (number) — This article is about the number. For other uses, see 22 (disambiguation). ← 21 23 → 22 ← 20 21 22 …
17Centered square number — In elementary number theory, a centered square number is a centered figurate number that gives the number of dots in a square with a dot in the center and all other dots surrounding the center dot in successive square layers. That is, each… …
18181 (number) — 181 is the natural number between 180 and 182.In mathematics181 is a prime number, and a twin prime with 179, making 181 a Chen prime. In base 10, it is a palindromic prime and a strobogrammatic prime.181 is not a regular polygonal number in any… …
19Nonagonal number — A nonagonal number or enneagonal number is a polygonal number that represents a nonagon. The nonagonal number for n is given by the formula: The first few nonagonal numbers are: 1, 9, 24, 46, 75, 111, 154, 204, 261, 325, 396, 474, 559, 651, 750,… …
20616 (number) — 616 ( six hundred and sixteen , or six hundred sixteen in American English) is believed by some Christians to have been the original Number of the Beast in the Book of Revelation in the Christian Bible. Different early versions of the Book of… …
