请输入您要查询的字词:

 

单词 UnusualNumber
释义

unusual number


An unusual numberMathworldPlanetmath or n-rough numberMathworldPlanetmath n is an integer with a greatest prime factor exceeding n. For example, the greatest prime factor of 102 is 17, which is greater than 11 (the square root of 102 rounded up to the next higher integer). The first few unusual numbers are 2, 3, 5, 6, 7, 10, 11, 13, 14, 15, 17, 19, 20, 21, 22, 23, 26, 28, 29, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 44, 46, 47, etc., listed in A064052 of Sloane’s OEIS. In fact, Donald Knuth and Donald Greene, who coined the term “unusual number,” remark that these numbers occur so frequently they’re not all that unusual. Unusual numbers include all of the prime numbersMathworldPlanetmath and many composites. Richard Schroeppel proved in HAKMEM 239 that the probability that a random integer is unusual is log2 (about 0.69314718).

References

  • 1 Donald Greene & Donald Knuth, Mathematics for the Analysis of Algorithms, 3rd edition. Boston: Birkhäuser (1990): 95 - 98
随便看

 

数学辞典收录了18232条数学词条,基本涵盖了常用数学知识及数学英语单词词组的翻译及用法,是数学学习的有利工具。

 

Copyright © 2000-2023 Newdu.com.com All Rights Reserved
更新时间:2025/5/4 9:25:34