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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. Divisor summatory function - Wikipedia

    en.wikipedia.org/wiki/Divisor_summatory_function

    In number theory, the divisor summatory function is a function that is a sum over the divisor function. It frequently occurs in the study of the asymptotic behaviour of the Riemann zeta function . The various studies of the behaviour of the divisor function are sometimes called divisor problems .

  4. Ramanujan's sum - Wikipedia

    en.wikipedia.org/wiki/Ramanujan's_sum

    Thus, the Ramanujan sum c q (n) ... is the divisor function (i.e. the sum of the k-th powers of the divisors of n, including 1 and n).

  5. Divisor sum identities - Wikipedia

    en.wikipedia.org/wiki/Divisor_sum_identities

    The purpose of this page is to catalog new, interesting, and useful identities related to number-theoretic divisor sums, i.e., sums of an arithmetic function over the divisors of a natural number , or equivalently the Dirichlet convolution of an arithmetic function () with one:

  6. Clifford's theorem on special divisors - Wikipedia

    en.wikipedia.org/wiki/Clifford's_theorem_on...

    A divisor on a Riemann surface C is a formal sum = of points P on C with integer coefficients. One considers a divisor as a set of constraints on meromorphic functions in the function field of C, defining () as the vector space of functions having poles only at points of D with positive coefficient, at most as bad as the coefficient indicates, and having zeros at points of D with negative ...

  7. Euclid–Euler theorem - Wikipedia

    en.wikipedia.org/wiki/Euclid–Euler_theorem

    Euler's proof is short [1] and depends on the fact that the sum of divisors function σ is multiplicative; that is, if a and b are any two relatively prime integers, then σ(ab) = σ(a)σ(b). For this formula to be valid, the sum of divisors of a number must include the number itself, not just the proper divisors.

  8. 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 ...

  9. Superabundant number - Wikipedia

    en.wikipedia.org/wiki/Superabundant_number

    In mathematics, a superabundant number is a certain kind of natural number.A natural number n is called superabundant precisely when, for all m < n: < ()where σ denotes the sum-of-divisors function (i.e., the sum of all positive divisors of n, including n itself).