# Triangular numbers

- Triangular Tri*an"gu*lar, a. [L. triangularis: cf. F.
triangulaire.]
1. Having three angles; having the form of a triangle.
[1913 Webster]
2. (Bot.) Oblong or elongated, and having three lateral angles; as, a triangular seed, leaf, or stem. [1913 Webster]

{Triangular compasses}, compasses with three legs for taking off the angular points of a triangle, or any three points at the same time.

{Triangular crab} (Zo["o]l.), any maioid crab; -- so called because the carapace is usually triangular.

{Triangular numbers} (Math.), the series of numbers formed by the successive sums of the terms of an arithmetical progression, of which the first term and the common difference are 1. See {Figurate numbers}, under {Figurate}. [1913 Webster]

*The Collaborative International Dictionary of English.
2000.*

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**triangular numbers**— noun plural : the successive sums n(n + 1)/2 where n = 1, 2, 3, ... of the first n natural numbers 1, 3, 6, 10, 15, … representable by dots arranged in triangles … Useful english dictionary**Triangular**— Tri*an gu*lar, a. [L. triangularis: cf. F. triangulaire.] 1. Having three angles; having the form of a triangle. [1913 Webster] 2. (Bot.) Oblong or elongated, and having three lateral angles; as, a triangular seed, leaf, or stem. [1913 Webster]… … The Collaborative International Dictionary of English**Triangular compasses**— Triangular Tri*an gu*lar, a. [L. triangularis: cf. F. triangulaire.] 1. Having three angles; having the form of a triangle. [1913 Webster] 2. (Bot.) Oblong or elongated, and having three lateral angles; as, a triangular seed, leaf, or stem. [1913 … The Collaborative International Dictionary of English**Triangular crab**— Triangular Tri*an gu*lar, a. [L. triangularis: cf. F. triangulaire.] 1. Having three angles; having the form of a triangle. [1913 Webster] 2. (Bot.) Oblong or elongated, and having three lateral angles; as, a triangular seed, leaf, or stem. [1913 … The Collaborative International Dictionary of English**Triangular 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;… … Wikipedia**Triangular array**— Not to be confused with Triangular matrix. The triangular array whose right hand diagonal sequence consists of Bell numbers In mathematics and computing, a triangular array of numbers, polynomials, or the like, is a doubly indexed sequence in… … Wikipedia**Triangular matrix**— In the mathematical discipline of linear algebra, a triangular matrix is a special kind of square matrix where the entries either below or above the main diagonal are zero. Because matrix equations with triangular matrices are easier to solve… … Wikipedia**Numbers in Norse mythology**— The numbers three and nine are significant numbers in Norse mythology and paganism. Both numbers (and multiplications thereof) appear throughout surviving attestations of Norse paganism, in both mythology and cultic practice.[1] While the number… … Wikipedia**Numbers in Germanic paganism**— The numbers three and nine are significant numbers in Germanic paganism and later Norse mythology. Both numbers (and multiplications thereof) appear throughout surviving attestations of Germanic paganism, in both Germanic mythology and religious… … Wikipedia**triangular number**— noun Any integer that is the sum of n natural numbers between 1 and n. Ten is a triangular number being the sum of 1, 2, 3, and 4 … Wiktionary