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A tetrahedral number, or triangular pyramidal number, is a figurate number that represents a pyramid with a triangular base and three sides, called a tetrahedron. The n th tetrahedral number, Te n , is the sum of the first n triangular numbers , that is,
a number represented as a discrete r-dimensional regular geometric pattern of r-dimensional balls such as a polygonal number (for r = 2) or a polyhedral number (for r = 3). a member of the subset of the sets above containing only triangular numbers, pyramidal numbers , and their analogs in other dimensions.
286 is an even composite number with 3 prime factors. [1] 286 is in the smallest pair of nontotient anagrams with 268. [2] 286 is a tetrahedral number which means that represents a tetrahedron. [3] 286 is a sphenic number which means that it has exactly 3 prime factors. [4] 286 the first even pseudoprime to base 3. [5]
In mathematics, a centered tetrahedral number is a centered figurate number that represents a tetrahedron. That is, it counts the dots in a three-dimensional dot pattern with a single dot surrounded by tetrahedral shells. [1] The th centered tetrahedral number, starting at = for a single dot, is: [2] [3]
The 3-orthoscheme is a tetrahedron having two right angles at each of two vertices, so another name for it is birectangular tetrahedron. It is also called a quadrirectangular tetrahedron because it contains four right angles.
A triangular number or triangle number counts objects arranged in an equilateral triangle. Triangular numbers are a type of figurate number , other examples being square numbers and cube numbers . The n th triangular number is the number of dots in the triangular arrangement with n dots on each side, and is equal to the sum of the n natural ...
It is the smallest primitive abundant number, [5] and the first number to have an abundance of 2, followed by 104. [6] 20 is the length of a side of the fifth smallest right triangle that forms a primitive Pythagorean triple (20, 21, 29). [7] [a] It is the third tetrahedral number. [8]
The basic 3-dimensional element are the tetrahedron, quadrilateral pyramid, ... A polyhedron (dual) element has any number of vertices, edges and faces.