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  2. Cube (algebra) - Wikipedia

    en.wikipedia.org/wiki/Cube_(algebra)

    With even cubes, there is considerable restriction, for only 00, o 2, e 4, o 6 and e 8 can be the last two digits of a perfect cube (where o stands for any odd digit and e for any even digit). Some cube numbers are also square numbers; for example, 64 is a square number (8 × 8) and a cube number (4 × 4 × 4).

  3. Perfect number - Wikipedia

    en.wikipedia.org/wiki/Perfect_number

    In number theory, a perfect number is a positive integer that is equal to the sum of its positive proper divisors, that is, divisors excluding the number itself. [1] For instance, 6 has proper divisors 1, 2 and 3, and 1 + 2 + 3 = 6, so 6 is a perfect number. The next perfect number is 28, since 1 + 2 + 4 + 7 + 14 = 28.

  4. Euler brick - Wikipedia

    en.wikipedia.org/wiki/Euler_brick

    A perfect cuboid (also called a perfect Euler brick or perfect box) is an Euler brick whose space diagonal also has integer length. In other words, the following equation is added to the system of Diophantine equations defining an Euler brick: + + =, where g is the space diagonal.

  5. List of Mersenne primes and perfect numbers - Wikipedia

    en.wikipedia.org/wiki/List_of_Mersenne_primes...

    Perfect numbers are natural numbers that equal the sum of their positive proper divisors, which are divisors excluding the number itself. So, 6 is a perfect number because the proper divisors of 6 are 1, 2, and 3, and 1 + 2 + 3 = 6. [2] [4] Euclid proved c. 300 BCE that every prime expressed as M p = 2 p − 1 has a corresponding perfect number ...

  6. Golden ratio - Wikipedia

    en.wikipedia.org/wiki/Golden_ratio

    An easily programmed alternative using only integer arithmetic is to calculate two large consecutive Fibonacci numbers and divide them. The ratio of Fibonacci numbers ⁠ F 25001 {\displaystyle F_{25001}} ⁠ and ⁠ F 25000 {\displaystyle F_{25000}} ⁠ , each over ⁠ 5000 {\displaystyle 5000} ⁠ digits, yields over ⁠ 10,000 {\displaystyle ...

  7. Mental calculation - Wikipedia

    en.wikipedia.org/wiki/Mental_calculation

    The square of n (most easily calculated when n is between 26 and 74 inclusive) is (50 − n) 2 + 100(n − 25) In other words, the square of a number is the square of its difference from fifty added to one hundred times the difference of the number and twenty five. For example, to square 62: (−12) 2 + [(62-25) × 100] = 144 + 3,700 = 3,844

  8. Hall's conjecture - Wikipedia

    en.wikipedia.org/wiki/Hall's_conjecture

    In mathematics, Hall's conjecture is an open question on the differences between perfect squares and perfect cubes. It asserts that a perfect square y 2 and a perfect cube x 3 that are not equal must lie a substantial distance apart. This question arose from consideration of the Mordell equation in the theory of integer points on elliptic curves.

  9. Tetrahedral number - Wikipedia

    en.wikipedia.org/wiki/Tetrahedral_number

    Te 12 = 364 is the total number of gifts "my true love sent to me" during the course of all 12 verses of the carol, "The Twelve Days of Christmas". [3] The cumulative total number of gifts after each verse is also Te n for verse n. The number of possible KeyForge three-house combinations is also a tetrahedral number, Te n−2 where n is the ...