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Perfect number. In number theory, a perfect number is a positive integer that is equal to the sum of its positive proper divisors, that is, divisors excluding the number itself. For instance, 6 has proper divisors 1, 2 and 3, and 1 + 2 + 3 = 6, so 6 is a perfect number. The next perfect number is 28, since 1 + 2 + 4 + 7 + 14 = 28.
Glossary of mathematical symbols. A mathematical symbol is a figure or a combination of figures that is used to represent a mathematical object, an action on mathematical objects, a relation between mathematical objects, or for structuring the other symbols that occur in a formula. As formulas are entirely constituted with symbols of various ...
Composite numbers can be arranged into rectangles but prime numbers cannot. A composite number is a positive integer that can be formed by multiplying two smaller positive integers. Equivalently, it is a positive integer that has at least one divisor other than 1 and itself. [1][2] Every positive integer is composite, prime, or the unit 1, so ...
In mathematics, the Fibonacci sequence is a sequence in which each number is the sum of the two preceding ones. Numbers that are part of the Fibonacci sequence are known as Fibonacci numbers, commonly denoted Fn . Many writers begin the sequence with 0 and 1, although some authors start it from 1 and 1 [1][2] and some (as did Fibonacci) from 1 ...
For example, 3 is a Mersenne prime as it is a prime number and is expressible as 22 − 1. [1][2] The numbers p corresponding to Mersenne primes must themselves be prime, although the vast majority of primes p do not lead to Mersenne primes—for example, 211 − 1 = 2047 = 23 × 89. [3] Meanwhile, perfect numbers are natural numbers that equal ...
As of Unicode version 16.0, there are 155,063 characters with code points, covering 168 modern and historical scripts, as well as multiple symbol sets.This article includes the 1,062 characters in the Multilingual European Character Set 2 subset, and some additional related characters.
φ(n) is the number of positive integers not greater than n that are coprime with n. A000010. Lucas numbers L(n) 2, 1, 3, 4, 7, 11, 18, 29, 47, 76, ... L(n) = L(n − 1) + L(n − 2) for n ≥ 2, with L(0) = 2 and L(1) = 1. A000032. Prime numbers pn. 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, ... The prime numbers pn, with n ≥ 1.
The centimetre (SI symbol: cm) is a unit of length in the metric system equal to 10−2 metres ( 1 100 m = 0.01 m). To help compare different orders of magnitude, this section lists lengths between 10 −2 m and 10 −1 m (1 cm and 1 dm). 1 cm – 10 millimetres. 1 cm – 0.39 inches. 1 cm – edge of a square of area 1 cm 2.