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  2. Parity (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Parity_(mathematics)

    Even and odd numbers have opposite parities, e.g., 22 (even number) and 13 (odd number) have opposite parities. In particular, the parity of zero is even. [2] Any two consecutive integers have opposite parity. A number (i.e., integer) expressed in the decimal numeral system is even or odd according to whether its last digit is even or odd. That ...

  3. Twin prime - Wikipedia

    en.wikipedia.org/wiki/Twin_prime

    Every third odd number is divisible by 3, and therefore no three successive odd numbers can be prime unless one of them is 3. Therefore, 5 is the only prime that is part of two twin prime pairs. The lower member of a pair is by definition a Chen prime. If m − 4 or m + 6 is also prime then the three primes are called a prime triplet.

  4. List of sums of reciprocals - Wikipedia

    en.wikipedia.org/wiki/List_of_sums_of_reciprocals

    The prime quadruplets are pairs of twin primes with only one odd number between them. The sum of the reciprocals of the numbers in prime quadruplets is approximately 0.8706. The sum of the reciprocals of the perfect powers (including duplicates) is 1. The sum of the reciprocals of the perfect powers (excluding duplicates) is approximately 0. ...

  5. Polite number - Wikipedia

    en.wikipedia.org/wiki/Polite_number

    A Young diagram representing visually a polite expansion 15 = 4 + 5 + 6. In number theory, a polite number is a positive integer that can be written as the sum of two or more consecutive positive integers.

  6. Interprime - Wikipedia

    en.wikipedia.org/wiki/Interprime

    In mathematics, an interprime is the average of two consecutive odd primes. [1] For example, 9 is an interprime because it is the average of 7 and 11. The first interprimes are:

  7. Ulam number - Wikipedia

    en.wikipedia.org/wiki/Ulam_number

    The idea can be generalized as (u, v)-Ulam numbers by selecting different starting values (u, v). A sequence of (u, v)-Ulam numbers is regular if the sequence of differences between consecutive numbers in the sequence is eventually periodic. When v is an odd number greater than three, the (2, v)-Ulam numbers are regular.

  8. Table of prime factors - Wikipedia

    en.wikipedia.org/wiki/Table_of_prime_factors

    An odd number does not have the prime factor 2. The first: 1, 3, 5, 7, 9, 11, ... A Ruth-Aaron pair is two consecutive numbers (x, x+1) with a 0 (x) = a 0 (x+1).

  9. Goldbach's weak conjecture - Wikipedia

    en.wikipedia.org/wiki/Goldbach's_weak_conjecture

    For if every even number greater than 4 is the sum of two odd primes, adding 3 to each even number greater than 4 will produce the odd numbers greater than 7 (and 7 itself is equal to 2+2+3). In 2013, Harald Helfgott released a proof of Goldbach's weak conjecture. [ 2 ]