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Let a be an integer that is not a square number and not −1. Write a = a 0 b 2 with a 0 square-free. Denote by S(a) the set of prime numbers p such that a is a primitive root modulo p. Then the conjecture states S(a) has a positive asymptotic density inside the set of primes. In particular, S(a) is infinite.
A number n is odd if there is an integer k such that n = 2k + 1. One way to prove that zero is not odd is by contradiction: if 0 = 2k + 1 then k = −1/2, which is not an integer. [15] Since zero is not odd, if an unknown number is proven to be odd, then it cannot be zero.
Legendre's conjecture, proposed by Adrien-Marie Legendre, states that there is a prime number between and (+) for every positive integer. [1] The conjecture is one of Landau's problems (1912) on prime numbers, and is one of many open problems on the spacing of prime numbers.
If really is prime, it will always answer yes, but if is composite then it answers yes with probability at most 1/2 and no with probability at least 1/2. [132] If this test is repeated n {\displaystyle n} times on the same number, the probability that a composite number could pass the test every time is at most 1 / 2 ...
Chen's theorem, another weakening of Goldbach's conjecture, proves that for all sufficiently large n, = + where p is prime and q is either prime or semiprime. [note 1] Bordignon, Johnston, and Starichkova, [5] correcting and improving on Yamada, [6] proved an explicit version of Chen's theorem: every even number greater than , is the sum of a ...
The prime number theorem asserts that an integer m selected at random has roughly a 1 / ln m chance of being prime. Thus if n is a large even integer and m is a number between 3 and n / 2 , then one might expect the probability of m and n − m simultaneously being prime to be 1 / ln m ln(n − m) .
We continue recursively in this manner until we reach a number known to be prime, such as 2. We end up with a tree of prime numbers, each associated with a witness a. For example, here is a complete Pratt certificate for the number 229: 229 (a = 6, 229 − 1 = 2 2 × 3 × 19), 2 (known prime), 3 (a = 2, 3 − 1 = 2), 2 (known prime),
Not all Euclid numbers are prime. E 6 = 13# + 1 = 30031 = 59 × 509 is the first composite Euclid number.. Every Euclid number is congruent to 3 modulo 4 since the primorial of which it is composed is twice the product of only odd primes and thus congruent to 2 modulo 4.