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  2. Primality test - Wikipedia

    en.wikipedia.org/wiki/Primality_test

    where f k is the k-th Fibonacci number. The first condition is the Fermat primality test using base 2. In general, if p ≡ a (mod x 2 +4), where a is a quadratic non-residue (mod x 2 +4) then p should be prime if the following conditions hold: 2 p−1 ≡ 1 (mod p), f(1) p+1 ≡ 0 (mod p), f(x) k is the k-th Fibonacci polynomial at x.

  3. Bounds checking - Wikipedia

    en.wikipedia.org/wiki/Bounds_checking

    A limited number of later CPUs have specialised instructions for checking bounds, e.g., the CHK2 instruction on the Motorola 68000 series. Research has been underway since at least 2005 regarding methods to use x86's built-in virtual memory management unit to ensure safety of array and buffer accesses. [ 4 ]

  4. Perfect digit-to-digit invariant - Wikipedia

    en.wikipedia.org/wiki/Perfect_digit-to-digit...

    Let be a natural number which can be written in base as the k-digit number ... where each digit is between and inclusive, and = =.We define the function : as () = =. (As 0 0 is usually undefined, there are typically two conventions used, one where it is taken to be equal to one, and another where it is taken to be equal to zero.

  5. Collatz conjecture - Wikipedia

    en.wikipedia.org/wiki/Collatz_conjecture

    f k (2 k a + b) = 3 c(b, k) a + d(b, k). The values of c (or better 3 c) and d can be precalculated for all possible k-bit numbers b, where d(b, k) is the result of applying the f function k times to b, and c(b, k) is the number of odd numbers encountered on the way. [30]

  6. List of integer sequences - Wikipedia

    en.wikipedia.org/wiki/List_of_integer_sequences

    A number that has the same number of digits as the number of digits in its prime factorization, including exponents but excluding exponents equal to 1. A046758 Extravagant numbers

  7. Modular arithmetic - Wikipedia

    en.wikipedia.org/wiki/Modular_arithmetic

    Primitive root modulo m: A number g is a primitive root modulo m if, for every integer a coprime to m, there is an integer k such that g k ≡ a (mod m). A primitive root modulo m exists if and only if m is equal to 2, 4, p k or 2p k, where p is an odd prime number and k is a positive integer.

  8. Goldbach's conjecture - Wikipedia

    en.wikipedia.org/wiki/Goldbach's_conjecture

    The prime number theorem asserts that an integer m selected at random has roughly a ⁠ 1 / ln m ⁠ chance of being prime. Thus if n is a large even integer and m is a number between 3 and ⁠ n / 2 ⁠, then one might expect the probability of m and n − m simultaneously being prime to be ⁠ 1 / ln m ln(n − m) ⁠.

  9. Smooth number - Wikipedia

    en.wikipedia.org/wiki/Smooth_number

    In number theory, an n-smooth (or n-friable) number is an integer whose prime factors are all less than or equal to n. [1] [2] For example, a 7-smooth number is a number in which every prime factor is at most 7. Therefore, 49 = 7 2 and 15750 = 2 × 3 2 × 5 3 × 7 are both 7-smooth, while 11 and 702 = 2 × 3 3 × 13 are not 7-smooth.