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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]
That is, is a quadratic residue precisely if the number of solutions of this equation is divisible by . And this equation can be solved in just the same way here as over the rational numbers: substitute x = a + 1 , y = a t + 1 {\displaystyle x=a+1,y=at+1} , where we demand that a ≠ 0 {\displaystyle a\neq 0} (leaving out the two solutions ( 1 ...
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]
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) .
We can find quadratic residues or verify them using the above formula. To test if 2 is a quadratic residue modulo 17, we calculate 2 (17 − 1)/2 = 2 8 ≡ 1 (mod 17), so it is a quadratic residue. To test if 3 is a quadratic residue modulo 17, we calculate 3 (17 − 1)/2 = 3 8 ≡ 16 ≡ −1 (mod 17), so it is not a quadratic residue.
The previous result says that a solution exists if and only if gcd(a, m) = 1, that is, a and m must be relatively prime (i.e. coprime). Furthermore, when this condition holds, there is exactly one solution, i.e., when it exists, a modular multiplicative inverse is unique: [ 8 ] If b and b' are both modular multiplicative inverses of a respect ...
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).
The values that a cyclotomic polynomial () may take for other integer values of x is strongly related with the multiplicative order modulo a prime number. More precisely, given a prime number p and an integer b coprime with p, the multiplicative order of b modulo p, is the smallest positive integer n such that p is a divisor of