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  2. Undefined (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Undefined_(mathematics)

    Contrast the term primitive notion, which is a core concept not defined in terms of other concepts. Primitive notions are used as building blocks to define other concepts. Contrast also the term undefined behavior in computer science, in which the term indicates that a function may produce or return any result, which may or may not be correct.

  3. Primitive abundant number - Wikipedia

    en.wikipedia.org/wiki/Primitive_abundant_number

    [1] [2] For example, 20 is a primitive abundant number because: The sum of its proper divisors is 1 + 2 + 4 + 5 + 10 = 22, so 20 is an abundant number. The sums of the proper divisors of 1, 2, 4, 5 and 10 are 0, 1, 3, 1 and 8 respectively, so each of these numbers is a deficient number. The first few primitive abundant numbers are:

  4. Primitive polynomial (field theory) - Wikipedia

    en.wikipedia.org/wiki/Primitive_polynomial...

    A primitive polynomial must have a non-zero constant term, for otherwise it will be divisible by x. Over GF(2), x + 1 is a primitive polynomial and all other primitive polynomials have an odd number of terms, since any polynomial mod 2 with an even number of terms is divisible by x + 1 (it has 1 as a root).

  5. Aliquot sequence - Wikipedia

    en.wikipedia.org/wiki/Aliquot_sequence

    The aliquot sequence starting with a positive integer k can be defined formally in terms of the sum-of-divisors function σ 1 or the aliquot sum function s in the following way: [1] = = = > = = = If the s n-1 = 0 condition is added, then the terms after 0 are all 0, and all aliquot sequences would be infinite, and we can conjecture that all aliquot sequences are convergent, the limit of these ...

  6. Practical number - Wikipedia

    en.wikipedia.org/wiki/Practical_number

    The only odd practical number is 1, because if is an odd number greater than 2, then 2 cannot be expressed as the sum of distinct divisors of . More strongly, Srinivasan (1948) observes that other than 1 and 2, every practical number is divisible by 4 or 6 (or both).

  7. Root of unity modulo n - Wikipedia

    en.wikipedia.org/wiki/Root_of_unity_modulo_n

    In number theory, a kth root of unity modulo n for positive integers k, n ≥ 2, is a root of unity in the ring of integers modulo n; that is, a solution x to the equation (or congruence) (). If k is the smallest such exponent for x, then x is called a primitive kth root of unity modulo n. [1]

  8. Zsigmondy's theorem - Wikipedia

    en.wikipedia.org/wiki/Zsigmondy's_theorem

    In number theory, Zsigmondy's theorem, named after Karl Zsigmondy, states that if > > are coprime integers, then for any integer , there is a prime number p (called a primitive prime divisor) that divides and does not divide for any positive integer <, with the following exceptions:

  9. 1 − 2 + 4 − 8 + ⋯ - ⋯ - Wikipedia

    en.wikipedia.org/wiki/1_%E2%88%92_2_%2B_4_%E2%88...

    In mathematics, 1 − 2 + 4 − 8 + ⋯ is the infinite series whose terms are the successive powers of two with alternating signs. As a geometric series, it is characterized by its first term, 1, and its common ratio, −2. = As a series of real numbers, it diverges. So in the usual sense it has no sum.