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  2. Reciprocals of primes - Wikipedia

    en.wikipedia.org/wiki/Reciprocals_of_primes

    A prime p (where p ≠ 2, 5 when working in base 10) is called unique if there is no other prime q such that the period length of the decimal expansion of its reciprocal, 1/p, is equal to the period length of the reciprocal of q, 1/q. [8]

  3. Divergence of the sum of the reciprocals of the primes

    en.wikipedia.org/wiki/Divergence_of_the_sum_of...

    The sum of the reciprocals of all prime numbers diverges; that is: = + + + + + + + = This was proved by Leonhard Euler in 1737, [ 1 ] and strengthens Euclid 's 3rd-century-BC result that there are infinitely many prime numbers and Nicole Oresme 's 14th-century proof of the divergence of the sum of the reciprocals of the integers (harmonic series) .

  4. List of sums of reciprocals - Wikipedia

    en.wikipedia.org/wiki/List_of_sums_of_reciprocals

    A "powerful number" is a positive integer for which every prime appearing in its prime factorization appears there at least twice. The sum of the reciprocals of the powerful numbers is close to 1.9436 . [4] The reciprocals of the factorials sum to the transcendental number e (one of two constants called "Euler's number").

  5. Formula for primes - Wikipedia

    en.wikipedia.org/wiki/Formula_for_primes

    Because the set of primes is a computably enumerable set, by Matiyasevich's theorem, it can be obtained from a system of Diophantine equations. Jones et al. (1976) found an explicit set of 14 Diophantine equations in 26 variables, such that a given number k + 2 is prime if and only if that system has a solution in nonnegative integers: [7]

  6. Brun's theorem - Wikipedia

    en.wikipedia.org/wiki/Brun's_theorem

    The convergence to Brun's constant. In number theory, Brun's theorem states that the sum of the reciprocals of the twin primes (pairs of prime numbers which differ by 2) converges to a finite value known as Brun's constant, usually denoted by B 2 (sequence A065421 in the OEIS).

  7. Harmonic number - Wikipedia

    en.wikipedia.org/wiki/Harmonic_number

    Harmonic numbers are related to the harmonic mean in that the n-th harmonic number is also n times the reciprocal of the ... all prime numbers ... of this formula.

  8. Quadratic reciprocity - Wikipedia

    en.wikipedia.org/wiki/Quadratic_reciprocity

    Gauss published the first and second proofs of the law of quadratic reciprocity on arts 125–146 and 262 of Disquisitiones Arithmeticae in 1801.. In number theory, the law of quadratic reciprocity is a theorem about modular arithmetic that gives conditions for the solvability of quadratic equations modulo prime numbers.

  9. List of prime numbers - Wikipedia

    en.wikipedia.org/wiki/List_of_prime_numbers

    This is a list of articles about prime numbers. A prime number (or prime) is a natural number greater than 1 that has no positive divisors other than 1 and itself. By Euclid's theorem, there are an infinite number of prime numbers. Subsets of the prime numbers may be generated with various formulas for primes.