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The prime constant is the real number whose th binary digit is 1 if is prime and 0 if ''n'' is composite or 1. In other words, is simply the number whose binary expansion corresponds to the indicator function of the set of prime numbers. That is, : where indicates a prime and is the characteristic function of the primes. The beginning of the decimal expansion of ''ρ'' is: The beginning of the binary expansion is: ==Irrationality== The number is easily shown to be irrational. To see why, suppose it were rational. Denote the th digit of the binary expansion of by . Then, since is assumed rational, there must exist , positive integers such that for all and all . Since there are an infinite number of primes, we may choose a prime . By definition we see that . As noted, we have for all . Now consider the case . We have , since is composite because . Since we see that 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「Prime constant」の詳細全文を読む スポンサード リンク
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