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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク refactorable number ： ウィキペディア英語版 refactorable number A refactorable number or tau number is an integer ''n'' that is divisible by the count of its divisors, or to put it algebraically, ''n'' is such that $\backslash tau(n)|n$. The first few refactorable numbers are listed in 1, 2, 8, 9, 12, 18, 24, 36, 40, 56, 60, 72, 80, 84, 88, 96, 104, 108, 128, 132, 136, 152, 156, 180, 184, 204, 225, 228, 232, 240, 248, 252, 276, 288, 296, ... For example, 18 has 6 divisors (1 and 18, 2 and 9, 3 and 6) and is divisible by 6. Cooper and Kennedy proved that refactorable numbers have natural density zero. Zelinsky proved that no three consecutive integers can all be refactorable.〔J. Zelinsky, "(Tau Numbers: A Partial Proof of a Conjecture and Other Results )," ''Journal of Integer Sequences'', Vol. 5 (2002), Article 02.2.8〕 Colton proved that no refactorable number is perfect. The equation GCD(''n'', ''x'') = τ(''n'') has solutions only if ''n'' is a refactorable number. There are still unsolved problems regarding refactorable numbers. Colton asked if there are there arbitrarily large ''n'' such that both ''n'' and ''n'' + 1 are refactorable. Zelinsky wondered if there exists a refactorable number $n\_0\; \backslash equiv\; a\; \backslash mod\; m$, does there necessarily exist $n\; >\; n\_0$ such that ''n'' is refactorable and $n\; \backslash equiv\; a\; \backslash mod\; m$. ==History== First defined by Curtis Cooper and Robert E. Kennedy〔 Cooper, C.N. and Kennedy, R. E. "Tau Numbers, Natural Density, and Hardy and Wright's Theorem 437." Internat. J. Math. Math. Sci. 13, 383-386, 1990 〕 where they showed that the tau numbers has natural density zero, they were later rediscovered by Simon Colton using a computer program he had made which invents and judges definitions from a variety of areas of mathematics such as number theory and graph theory.〔S. Colton, "(Refactorable Numbers - A Machine Invention )," ''Journal of Integer Sequences'', Vol. 2 (1999), Article 99.1.2〕 Colton called such numbers "refactorable". While computer programs had discovered proofs before, this discovery was one of the first times that a computer program had discovered a new or previously obscure idea. Colton proved many results about refactorable numbers, showing that there were infinitely many and proving a variety of congruence restrictions on their distribution. Colton was only later alerted that Kennedy and Cooper had previously investigated the topic. 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「refactorable number」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.