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  2. Practical number - Wikipedia

    en.wikipedia.org/wiki/Practical_number

    The proof involves finding a sequence of practical numbers with the property that every number less than may be written as a sum of (⁡) distinct divisors of . Then, i {\displaystyle i} is chosen so that n i − 1 < y < n i {\displaystyle n_{i-1}<y<n_{i}} , and x n i {\displaystyle xn_{i}} is divided by y {\displaystyle y} giving quotient q ...

  3. Number - Wikipedia

    en.wikipedia.org/wiki/Number

    In mathematics, the notion of number has been extended over the centuries to include zero (0), [3] negative numbers, [4] rational numbers such as one half (), real numbers such as the square root of 2 and π, [5] and complex numbers [6] which extend the real numbers with a square root of −1 (and its combinations with real numbers by adding or ...

  4. Natural logarithm of 2 - Wikipedia

    en.wikipedia.org/wiki/Natural_logarithm_of_2

    In a third layer, the logarithms of rational numbers r = ⁠ a / b ⁠ are computed with ln(r) = ln(a) − ln(b), and logarithms of roots via ln n √ c = ⁠ 1 / n ⁠ ln(c).. The logarithm of 2 is useful in the sense that the powers of 2 are rather densely distributed; finding powers 2 i close to powers b j of other numbers b is comparatively easy, and series representations of ln(b) are ...

  5. Mathematics - Wikipedia

    en.wikipedia.org/wiki/Mathematics

    Algebra became an area in its own right only with François Viète (1540–1603), who introduced the use of variables for representing unknown or unspecified numbers. [33] Variables allow mathematicians to describe the operations that have to be done on the numbers represented using mathematical formulas. [34]

  6. Prime-counting function - Wikipedia

    en.wikipedia.org/wiki/Prime-counting_function

    In mathematics, the prime-counting function is the function counting the number of prime numbers less than or equal to some real number x. [1] [2] It is denoted by π(x) (unrelated to the number π). A symmetric variant seen sometimes is π 0 (x), which is equal to π(x) − 1 ⁄ 2 if x is exactly a prime number, and equal to π(x) otherwise.

  7. Fibonacci sequence - Wikipedia

    en.wikipedia.org/wiki/Fibonacci_sequence

    Moreover, every positive integer can be written in a unique way as the sum of one or more distinct Fibonacci numbers in such a way that the sum does not include any two consecutive Fibonacci numbers. This is known as Zeckendorf's theorem , and a sum of Fibonacci numbers that satisfies these conditions is called a Zeckendorf representation.

  8. Proof by infinite descent - Wikipedia

    en.wikipedia.org/wiki/Proof_by_infinite_descent

    In mathematics, a proof by infinite descent, also known as Fermat's method of descent, is a particular kind of proof by contradiction [1] used to show that a statement cannot possibly hold for any number, by showing that if the statement were to hold for a number, then the same would be true for a smaller number, leading to an infinite descent and ultimately a contradiction. [2]

  9. Quaternary numeral system - Wikipedia

    en.wikipedia.org/wiki/Quaternary_numeral_system

    As with the octal and hexadecimal numeral systems, quaternary has a special relation to the binary numeral system.Each radix four, eight, and sixteen is a power of two, so the conversion to and from binary is implemented by matching each digit with two, three, or four binary digits, or bits.