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In the field of number theory, the Brun sieve (also called Brun's pure sieve) is a technique for estimating the size of "sifted sets" of positive integers which satisfy a set of conditions which are expressed by congruences. It was developed by Viggo Brun in 1915. ==Description== In terms of sieve theory the Brun sieve is of ''combinatorial type''; that is, it derives from a careful use of the inclusion-exclusion principle. Let ''A'' be a set of positive integers ≤ ''x'' and let ''P'' be a set of primes. For each ''p'' in ''P'', let ''A''''p'' denote the set of elements of ''A'' divisible by ''p'' and extend this to let ''A''''d'' the intersection of the ''A''''p'' for ''p'' dividing ''d'', when ''d'' is a product of distinct primes from ''P''. Further let A1 denote ''A'' itself. Let ''z'' be a positive real number and ''P''(''z'') denote the primes in ''P'' ≤ ''z''. The object of the sieve is to estimate : We assume that |''A''''d''| may be estimated by : where ''w'' is a multiplicative function and ''X'' = |''A''|. Let : 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Brun sieve」の詳細全文を読む スポンサード リンク
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