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  2. Betrothed numbers - Wikipedia

    en.wikipedia.org/wiki/Betrothed_numbers

    Quasi-sociable numbers or reduced sociable numbers are numbers whose aliquot sums minus one form a cyclic sequence that begins and ends with the same number. 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 ...

  3. Symbolab - Wikipedia

    en.wikipedia.org/wiki/Symbolab

    Symbolab is an answer engine [1] that provides step-by-step solutions to mathematical problems in a range of subjects. [2] It was originally developed by Israeli start-up company EqsQuest Ltd., under whom it was released for public use in 2011. In 2020, the company was acquired by American educational technology website Course Hero. [3] [4]

  4. Betti number - Wikipedia

    en.wikipedia.org/wiki/Betti_number

    For a torus, the first Betti number is b 1 = 2 , which can be intuitively thought of as the number of circular "holes" Informally, the kth Betti number refers to the number of k-dimensional holes on a topological surface. A "k-dimensional hole" is a k-dimensional cycle that is not a boundary of a (k+1)-dimensional object.

  5. Amicable numbers - Wikipedia

    en.wikipedia.org/wiki/Amicable_numbers

    In mathematics, the amicable numbers are two different natural numbers related in such a way that the sum of the proper divisors of each is equal to the other number. That is, s ( a )= b and s ( b )= a , where s ( n )=σ( n )- n is equal to the sum of positive divisors of n except n itself (see also divisor function ).

  6. 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 ...

  7. WolframAlpha - Wikipedia

    en.wikipedia.org/wiki/WolframAlpha

    WolframAlpha gathers data from academic and commercial websites such as the CIA's The World Factbook, the United States Geological Survey, a Cornell University Library publication called All About Birds, Chambers Biographical Dictionary, Dow Jones, the Catalogue of Life, [1] CrunchBase, [10] Best Buy, [11] and the FAA to answer queries.

  8. Chisanbop - Wikipedia

    en.wikipedia.org/wiki/Chisanbop

    The Chisanbop system. When a finger is touching the table, it contributes its corresponding number to a total. Chisanbop or chisenbop (from Korean chi (ji) finger + sanpŏp (sanbeop) calculation [1] 지산법/指算法), sometimes called Fingermath, [2] is a finger counting method used to perform basic mathematical operations.

  9. Little Professor - Wikipedia

    en.wikipedia.org/wiki/Little_Professor

    The user has three chances to enter the correct number. If the answer is incorrect, the display shows "EEE". After the third wrong answer, the correct answer is shown. If the answer supplied is correct, the Little Professor goes to the next equation. [2] The Little Professor shows the number of correct first answers after each set of 10 ...