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  2. Factorial - Wikipedia

    en.wikipedia.org/wiki/Factorial

    In mathematics, the factorial of a non-negative integer, denoted by !, is the product of all positive integers less than or equal to . The factorial of also equals the product of with the next smaller factorial: ! = () = ()! For example, ! =! = =

  3. Full factorial experiment - Wikipedia

    en.wikipedia.org/wiki/Full_factorial_experiment

    The main effect of A is said to be absent if this expression equals 0. Interaction in a factorial experiment is the lack of additivity between factors, and is also expressed by contrasts. In the 2 × 3 experiment, the contrasts

  4. Factorion - Wikipedia

    en.wikipedia.org/wiki/Factorion

    A natural number is a sociable factorion if it is a periodic point for , where ⁡ = for a positive integer, and forms a cycle of period . A factorion is a sociable factorion with k = 1 {\displaystyle k=1} , and a amicable factorion is a sociable factorion with k = 2 {\displaystyle k=2} .

  5. Unit of time - Wikipedia

    en.wikipedia.org/wiki/Unit_of_time

    1/1000 d (0.001 d) 1.44 minutes, or 86.4 seconds. Also marketed as a ".beat" by the Swatch corporation. moment: 1/40 solar hour (90 s on average) Medieval unit of time used by astronomers to compute astronomical movements, length varies with the season. [4] Also colloquially refers to a brief period of time. centiday 0.01 d (1 % of a day)

  6. Glossary of mathematical symbols - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_mathematical...

    1. Factorial: if n is a positive integer, n! is the product of the first n positive integers, and is read as "n factorial". 2. Double factorial: if n is a positive integer, n!! is the product of all positive integers up to n with the same parity as n, and is read as "the double factorial of n". 3.

  7. List of time periods - Wikipedia

    en.wikipedia.org/wiki/List_of_time_periods

    It is the period in which Greek and Roman society flourished and wielded great influence throughout Europe, North Africa and the Middle East. Post-classical historyPeriod of time that immediately followed ancient history. Depending on the continent, the era generally falls between the years AD 200–600 and AD 1200–1500.

  8. Empty product - Wikipedia

    en.wikipedia.org/wiki/Empty_product

    For example, the empty products 0! = 1 (the factorial of zero) and x 0 = 1 shorten Taylor series notation (see zero to the power of zero for a discussion of when x = 0). Likewise, if M is an n × n matrix, then M 0 is the n × n identity matrix , reflecting the fact that applying a linear map zero times has the same effect as applying the ...

  9. Euler's totient function - Wikipedia

    en.wikipedia.org/wiki/Euler's_totient_function

    A perfect totient number is an integer that is equal to the sum of its iterated totients. That is, we apply the totient function to a number n, apply it again to the resulting totient, and so on, until the number 1 is reached, and add together the resulting sequence of numbers; if the sum equals n, then n is a perfect totient number.