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Sieve of Sundaram: algorithm steps for primes below 202 (unoptimized). The sieve starts with a list of the integers from 1 to n.From this list, all numbers of the form i + j + 2ij are removed, where i and j are positive integers such that 1 ≤ i ≤ j and i + j + 2ij ≤ n.
Sieve of Eratosthenes: algorithm steps for primes below 121 (including optimization of starting from prime's square). In mathematics, the sieve of Eratosthenes is an ancient algorithm for finding all prime numbers up to any given limit.
As shown in a sidebar table, the 0th element represented 3, 1st element 5, 2nd element 7, and so on. This is the original BASIC version of the code presented in 1981. [ 20 ] [ a ] The dialect is not specified, but a number of details mean it does not run under early versions of Microsoft BASIC (4.x and earlier), among these the use of long ...
[3] We start with some countable sequence of non-negative numbers A = ( a n ) {\displaystyle {\mathcal {A}}=(a_{n})} . In the most basic case this sequence is just the indicator function a n = 1 A ( n ) {\displaystyle a_{n}=1_{A}(n)} of some set A = { s : s ≤ x } {\displaystyle A=\{s:s\leq x\}} we want to sieve.
A prime sieve or prime number sieve is a fast type of algorithm for finding primes. There are many prime sieves. The simple sieve of Eratosthenes (250s BCE), the sieve of Sundaram (1934), the still faster but more complicated sieve of Atkin [1] (2003), sieve of Pritchard (1979), and various wheel sieves [2] are most common.
In this example the fact that the Legendre identity is derived from the Sieve of Eratosthenes is clear: the first term is the number of integers below X, the second term removes the multiples of all primes, the third term adds back the multiples of two primes (which were miscounted by being "crossed out twice") but also adds back the multiples ...
The following is pseudocode which combines Atkin's algorithms 3.1, 3.2, and 3.3 [1] by using a combined set s of all the numbers modulo 60 excluding those which are multiples of the prime numbers 2, 3, and 5, as per the algorithms, for a straightforward version of the algorithm that supports optional bit-packing of the wheel; although not specifically mentioned in the referenced paper, this ...
1 2 3 5. The first number after 1 for wheel 2 is 5; note it as a prime. Now form wheel 3 with length 5 × 6 = 30 by first extending wheel 2 up to 30 and then deleting 5 times each number in wheel 2 (in reverse order!), to get 1 2 3 5 7 11 13 17 19 23 25 29. The first number after 1 for wheel 3 is 7; note it as a prime.