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  2. Goldbach's conjecture - Wikipedia

    en.wikipedia.org/wiki/Goldbach's_conjecture

    In 1975, Hugh Lowell Montgomery and Bob Vaughan showed that "most" even numbers are expressible as the sum of two primes. More precisely, they showed that there exist positive constants c and C such that for all sufficiently large numbers N, every even number less than N is the sum of two primes, with at most CN 1 − c exceptions.

  3. List of sums of reciprocals - Wikipedia

    en.wikipedia.org/wiki/List_of_sums_of_reciprocals

    The purpose of this restriction is to preclude the known infinitude of solutions in which two exponents are 2 and the other exponent is any even number. The n-th harmonic number, which is the sum of the reciprocals of the first n positive integers, is never an integer except for the case n = 1.

  4. Summation - Wikipedia

    en.wikipedia.org/wiki/Summation

    In mathematics, summation is the addition of a sequence of numbers, called addends or summands; the result is their sum or total.Beside numbers, other types of values can be summed as well: functions, vectors, matrices, polynomials and, in general, elements of any type of mathematical objects on which an operation denoted "+" is defined.

  5. List of prime numbers - Wikipedia

    en.wikipedia.org/wiki/List_of_prime_numbers

    A cluster prime is a prime p such that every even natural number k ≤ p − 3 is the difference of two primes not exceeding p. 3, 5, 7, 11, 13, 17, 19, 23, ... (OEIS: A038134) All odd primes between 3 and 89, inclusive, are cluster primes. The first 10 primes that are not cluster primes are: 2, 97, 127, 149, 191, 211, 223, 227, 229, 251.

  6. 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]

  7. Perfect number - Wikipedia

    en.wikipedia.org/wiki/Perfect_number

    The first four perfect numbers are 6, 28, 496 and 8128. [1] ... 28 is also the only even perfect number that is a sum of two positive cubes of integers ...

  8. Chen's theorem - Wikipedia

    en.wikipedia.org/wiki/Chen's_theorem

    Every even number greater than can be represented as the sum of a prime and a square-free number with at most two prime factors. Also in 2022, Bordignon and Valeriia Starichkova [ 9 ] showed that the bound can be lowered to e e 15.85 ≈ 3.6 ⋅ 10 3321634 {\displaystyle e^{e^{15.85}}\approx 3.6\cdot 10^{3321634}} assuming the Generalized ...

  9. Pronic number - Wikipedia

    en.wikipedia.org/wiki/Pronic_number

    The n th pronic number is the sum of the first n even integers, and as such is twice the n th triangular number [1] [2] and n more than the n th square number, as given by the alternative formula n 2 + n for pronic numbers. Hence the n th pronic number and the n th square number (the sum of the first n odd integers) form a superparticular ratio: