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  2. 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 ...

  3. 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.

  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. 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.

  6. 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.

  7. Polignac's conjecture - Wikipedia

    en.wikipedia.org/wiki/Polignac's_conjecture

    In number theory, Polignac's conjecture was made by Alphonse de Polignac in 1849 and states: [1] For any positive even number n, there are infinitely many prime gaps of size n. In other words: There are infinitely many cases of two consecutive prime numbers with difference n. [2]

  8. Shapiro inequality - Wikipedia

    en.wikipedia.org/wiki/Shapiro_inequality

    Suppose n is a natural number and x 1, x 2, …, x n are positive numbers and: n is even and less than or equal to 12, or; n is odd and less than or equal to 23. Then the Shapiro inequality states that = + + +, where x n+1 = x 1 and x n+2 = x 2.

  9. Semiprime - Wikipedia

    en.wikipedia.org/wiki/Semiprime

    In mathematics, a semiprime is a natural number that is the product of exactly two prime numbers. The two primes in the product may equal each other, so the semiprimes include the squares of prime numbers. Because there are infinitely many prime numbers, there are also infinitely many semiprimes.