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  2. List of types of numbers - Wikipedia

    en.wikipedia.org/wiki/List_of_types_of_numbers

    Negative numbers: Real numbers that are less than zero. Because zero itself has no sign, neither the positive numbers nor the negative numbers include zero. When zero is a possibility, the following terms are often used: Non-negative numbers: Real numbers that are greater than or equal to zero. Thus a non-negative number is either zero or positive.

  3. Pólya conjecture - Wikipedia

    en.wikipedia.org/wiki/Pólya_conjecture

    The Pólya conjecture states that for any n > 1, if the natural numbers less than or equal to n (excluding 0) are partitioned into those with an odd number of prime factors and those with an even number of prime factors, then the former set has at least as many members as the latter set. Repeated prime factors are counted repeatedly; for ...

  4. Square-free integer - Wikipedia

    en.wikipedia.org/wiki/Square-free_integer

    In mathematics, a square-free integer (or squarefree integer) is an integer which is divisible by no square number other than 1. That is, its prime factorization has exactly one factor for each prime that appears in it. For example, 10 = 2 ⋅ 5 is square-free, but 18 = 2 ⋅ 3 ⋅ 3 is not, because 18 is divisible by 9 = 3 2. The smallest ...

  5. Sieve of Eratosthenes - Wikipedia

    en.wikipedia.org/wiki/Sieve_of_Eratosthenes

    A prime number is a natural number that has exactly two distinct natural number divisors: the number 1 and itself. To find all the prime numbers less than or equal to a given integer n by Eratosthenes' method: Create a list of consecutive integers from 2 through n: (2, 3, 4, ..., n). Initially, let p equal 2, the smallest prime number.

  6. Natural number - Wikipedia

    en.wikipedia.org/wiki/Natural_number

    It follows from the definition that each natural number is equal to the set of all natural numbers less than it. This definition, can be extended to the von Neumann definition of ordinals for defining all ordinal numbers, including the infinite ones: "each ordinal is the well-ordered set of all smaller ordinals."

  7. Mersenne conjectures - Wikipedia

    en.wikipedia.org/wiki/Mersenne_conjectures

    The New Mersenne conjecture or Bateman, Selfridge and Wagstaff conjecture (Bateman et al. 1989) states that for any odd natural number p, if any two of the following conditions hold, then so does the third: p = 2 k ± 1 or p = 4 k ± 3 for some natural number k. (OEIS: A122834) 2 p − 1 is prime (a Mersenne prime). (OEIS: A000043)

  8. Polignac's conjecture - Wikipedia

    en.wikipedia.org/wiki/Polignac's_conjecture

    In other words: There are infinitely many cases of two consecutive prime numbers with difference n. [ 2 ] Although the conjecture has not yet been proven or disproven for any given value of n , in 2013 an important breakthrough was made by Yitang Zhang who proved that there are infinitely many prime gaps of size n for some value of n < 70,000,000.

  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.