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Or to put it algebraically, writing the sequence of prime numbers as (p 1, p 2, p 3, ...) = (2, 3, 5, ...), p n is a strong prime if p n > p n − 1 + p n + 1 / 2 . For example, 17 is the seventh prime: the sixth and eighth primes, 13 and 19, add up to 32, and half that is 16; 17 is greater than 16, so 17 is a strong prime. The first few ...
These numbers have been proved prime by computer with a primality test for their form, for example the Lucas–Lehmer primality test for Mersenne numbers. “!” is the factorial, “#” is the primorial, and () is the third cyclotomic polynomial, defined as + +.
For example, there are only 13 numbers less than 25·10 9 that are strong pseudoprimes to bases 2, 3, and 5 simultaneously. They are listed in Table 7 of. [2] The smallest such number is 25326001. This means that, if n is less than 25326001 and n is a strong probable prime to bases 2, 3, and 5, then n is prime.
In C++, any class that can be three-way compared can be a parameter to instances of std::compare_three_way, std::strong_order, std::weak_order, or std::partial_order. Since Java version 1.5, the same can be computed using the Math.signum static method if the difference can be known without computational problems such as arithmetic overflow ...
For example, up to 25 × 10 9, there are 11,408,012,595 odd composite numbers, but only 21,853 pseudoprimes base 2. [1] ... The number n is a strong probable prime ...
A powerful number is a positive integer m such that for every prime number p dividing m, p 2 also divides m. Equivalently, a powerful number is the product of a square and a cube, that is, a number m of the form m = a 2 b 3, where a and b are positive integers. Powerful numbers are also known as squareful, square-full, or 2-full.
Pseudoprimes are of primary importance in public-key cryptography, which makes use of the difficulty of factoring large numbers into their prime factors. Carl Pomerance estimated in 1988 that it would cost $10 million to factor a number with 144 digits, and $100 billion to factor a 200-digit number (the cost today is dramatically lower but ...
As an example, 108 is a powerful number. Its prime factorization is 2 2 · 3 3, and thus its prime factors are 2 and 3.Both 2 2 = 4 and 3 2 = 9 are divisors of 108. However, 108 cannot be represented as m k, where m and k are positive integers greater than 1, so 108 is an Achilles number.