|
In mathematics, a sequence of positive integers ''a''''n'' is called an irrationality sequence if it has the property that, for every sequence ''x''''n'' of positive integers, the sum of the series : exists (that is, it converges) and is an irrational number.〔.〕〔.〕 The problem of characterizing irrationality sequences was posed by Paul Erdős and Ernst G. Straus, who originally called the property of being an irrationality sequence "Property P".〔.〕 ==Examples== The powers of two whose exponents are powers of two, , form an irrationality sequence. However, although Sylvester's sequence :2, 3, 7, 43, 1807, 3263443, ... (in which each term is one more than the product of all previous terms) also grows doubly exponentially, it does not form an irrationality sequence. For, letting gives : a series converging to a rational number. Likewise, the factorials do not form an irrationality sequence, because the sequence leads to a series with a rational sum, :〔 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「Irrationality sequence」の詳細全文を読む スポンサード リンク
|