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In mathematics, a series is the sum of the terms of a sequence of numbers. Given a sequence , the ''n''th partial sum is the sum of the first ''n'' terms of the sequence, that is, : A series is convergent if the sequence of its partial sums converges; in other words, it approaches a given number. In more formal language, a series converges if there exists a limit such that for any arbitrarily small positive number , there is a large integer such that for all , : Any series that is not convergent is said to be divergent. == Examples of convergent and divergent series == * The reciprocals of the positive integers produce a divergent series (harmonic series): *: * Alternating the signs of the reciprocals of positive integers produces a convergent series: *: * The reciprocals of prime numbers produce a divergent series (so the set of primes is "large"): *: * The reciprocals of triangular numbers produce a convergent series: *: * The reciprocals of factorials produce a convergent series (see e): *: * The reciprocals of square numbers produce a convergent series (the Basel problem): *: * The reciprocals of powers of 2 produce a convergent series (so the set of powers of 2 is "small"): *: * Alternating the signs of reciprocals of powers of 2 also produces a convergent series: *: * The reciprocals of Fibonacci numbers produce a convergent series (see ψ): *: 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「convergent series」の詳細全文を読む スポンサード リンク
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