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  2. 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

  3. 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.

  4. 68–95–99.7 rule - Wikipedia

    en.wikipedia.org/wiki/68–95–99.7_rule

    Diagram showing the cumulative distribution function for the normal distribution with mean (μ) 0 and variance (σ 2) 1. These numerical values "68%, 95%, 99.7%" come from the cumulative distribution function of the normal distribution. The prediction interval for any standard score z corresponds numerically to (1 − (1 − Φ μ,σ 2 (z)) · 2).

  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. 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 .

  7. 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 ...

  8. Standard deviation - Wikipedia

    en.wikipedia.org/wiki/Standard_deviation

    Standard deviation can also be used to calculate ... (because the square root is a nonlinear function ... Particle physics conventionally uses a standard of "5 sigma ...

  9. σ-algebra - Wikipedia

    en.wikipedia.org/wiki/Σ-algebra

    In mathematical analysis and in probability theory, a σ-algebra ("sigma algebra"; also σ-field, where the σ comes from the German "Summe" [1]) on a set X is a nonempty collection Σ of subsets of X closed under complement, countable unions, and countable intersections. The ordered pair (,) is called a measurable space.