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  2. Betrothed numbers - Wikipedia

    en.wikipedia.org/wiki/Betrothed_numbers

    They are generalizations of the concepts of betrothed numbers and quasiperfect numbers. The first quasi-sociable sequences, or quasi-sociable chains, were discovered by Mitchell Dickerman in 1997: 1215571544 = 2^3*11*13813313; 1270824975 = 3^2*5^2*7*19*42467; 1467511664 = 2^4*19*599*8059; 1530808335 = 3^3*5*7*1619903; 1579407344 = 2^4*31^2*59*1741

  3. Betti number - Wikipedia

    en.wikipedia.org/wiki/Betti_number

    Here, Z 2 is the cyclic group of order 2. The 0-th Betti number is again 1. However, the 1-st Betti number is 0. This is because H 1 (P) is a finite group - it does not have any infinite component. The finite component of the group is called the torsion coefficient of P.

  4. Sociable number - Wikipedia

    en.wikipedia.org/wiki/Sociable_number

    The period of the sequence, or order of the set of sociable numbers, is the number of numbers in this cycle. If the period of the sequence is 1, the number is a sociable number of order 1, or a perfect number—for example, the proper divisors of 6 are 1, 2, and 3, whose sum is again 6. A pair of amicable numbers is a set of sociable numbers of ...

  5. Genius (mathematics software) - Wikipedia

    en.wikipedia.org/wiki/Genius_(mathematics_software)

    Genius (also known as the Genius Math Tool) is a free open-source numerical computing environment and programming language, [2] similar in some aspects to MATLAB, GNU Octave, Mathematica and Maple. Genius is aimed at mathematical experimentation rather than computationally intensive tasks. It is also very useful as just a calculator.

  6. 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 ...

  7. Amicable numbers - Wikipedia

    en.wikipedia.org/wiki/Amicable_numbers

    where n > 1 is an integer and p, q, r are prime numbers, then 2 n × p × q and 2 n × r are a pair of amicable numbers. This formula gives the pairs (220, 284) for n = 2, (17296, 18416) for n = 4, and (9363584, 9437056) for n = 7, but no other such pairs are known. Numbers of the form 3 × 2 n − 1 are known as Thabit numbers.

  8. List of arbitrary-precision arithmetic software - Wikipedia

    en.wikipedia.org/wiki/List_of_arbitrary...

    Programming languages that support arbitrary precision computations, either built-in, or in the standard library of the language: Ada: the upcoming Ada 202x revision adds the Ada.Numerics.Big_Numbers.Big_Integers and Ada.Numerics.Big_Numbers.Big_Reals packages to the standard library, providing arbitrary precision integers and real numbers.

  9. Fortunate number - Wikipedia

    en.wikipedia.org/wiki/Fortunate_number

    Adding 2 to that gives another even number, while adding 3 would give another multiple of 3. One would similarly rule out the integers up to 18. Adding 19, however, gives 510529, which is prime. Hence 19 is a Fortunate number. The Fortunate number for p n # is always above p n and all its divisors are larger than p n. This is because p n #, and ...