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  2. Divisor function - Wikipedia

    en.wikipedia.org/wiki/Divisor_function

    Divisor function σ 0 (n) up to n = 250 Sigma function σ 1 (n) up to n = 250 Sum of the squares of divisors, σ 2 (n), up to n = 250 Sum of cubes of divisors, σ 3 (n) up to n = 250. In mathematics, and specifically in number theory, a divisor function is an arithmetic function related to the divisors of an integer.

  3. Normal distribution - Wikipedia

    en.wikipedia.org/wiki/Normal_distribution

    The moment generating function of a real random variable is the expected value of , as a function of the real parameter . For a normal distribution with density f {\textstyle f} , mean μ {\textstyle \mu } and variance σ 2 {\textstyle \sigma ^{2}} , the moment generating function exists and is equal to

  4. Sigma function - Wikipedia

    en.wikipedia.org/wiki/Sigma_function

    In mathematics, by sigma function one can mean one of the following: The sum-of-divisors function σ a ( n ), an arithmetic function Weierstrass sigma function , related to elliptic functions

  5. Sigmoid function - Wikipedia

    en.wikipedia.org/wiki/Sigmoid_function

    A wide variety of sigmoid functions including the logistic and hyperbolic tangent functions have been used as the activation function of artificial neurons. Sigmoid curves are also common in statistics as cumulative distribution functions (which go from 0 to 1), such as the integrals of the logistic density , the normal density , and Student's ...

  6. Colossally abundant number - Wikipedia

    en.wikipedia.org/wiki/Colossally_abundant_number

    Sigma function σ 1 (n) up to n = 250 Prime-power factors. In number theory, a colossally abundant number (sometimes abbreviated as CA) is a natural number that, in a particular, rigorous sense, has many divisors. Particularly, it is defined by a ratio between the sum of an integer's divisors and that integer raised to a power higher than one ...

  7. Sigma - Wikipedia

    en.wikipedia.org/wiki/Sigma

    In number theory, σ is included in various divisor functions, especially the sigma function or sum-of-divisors function. In applied mathematics , σ( T ) denotes the spectrum of a linear map T . In complex analysis , σ is used in the Weierstrass sigma-function .

  8. Sign function - Wikipedia

    en.wikipedia.org/wiki/Sign_function

    The signum function of a real number is a piecewise function which is defined as follows: [1] ⁡:= {<, =, > The law of trichotomy states that every real number must be positive, negative or zero. The signum function denotes which unique category a number falls into by mapping it to one of the values −1 , +1 or 0, which can then be used in ...

  9. Busy beaver - Wikipedia

    en.wikipedia.org/wiki/Busy_beaver

    The functions determining the highest score or longest running time of the n-state busy beavers by each definition are Σ(n) and S(n) respectively. [4] Deciding the running time or score of the nth Busy Beaver is incomputable. [4] In fact, both the functions Σ(n) and S(n) eventually become larger than any computable function. [4]