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本原过剩数

本原过剩数Primitive abundant number)也称为本原丰数,为一数学用语,是指一个整数本身为过剩数,而其真因数(小于本身的因数)均为亏数[1][2]。过剩数及完全数的倍数都会是过剩数,因此本原过剩数可视为除了过剩数及完全数的倍数之外的过剩数。

例如,数字20因为有以下的性质,因此是本原过剩数:

  1. 真因数的和为1 + 2 + 4 + 5 + 10 = 22,大于20,因此20为过剩数
  2. 真因数1, 2, 4, 5, 10的真因数和分别是0, 1, 3, 1, 8,因此其真因数均为亏数

头几个本原过剩数为:

20, 70, 88, 104, 272, 304, 368, 464, 550, 572 ... (OEIS数列A071395

奇数的本原过剩数中,最小的是945。

性质

  • 所有本原过剩数的倍数均为过剩数。
  • 所有过剩数都是本原过剩数或是完全数的倍数。
  • 本原过剩数共有无限多个。
  • 小于等于n的本原过剩数个数为[3]

参考资料

  1. ^ Weisstein, Eric W. (编). Primitive Abundant Number. at MathWorld--A Wolfram Web Resource. Wolfram Research, Inc. (英语). 
  2. ^ Erdős有另外一个本原过剩数的定义,允许完全数也可视为本原丰数,此定义下本原过剩数不一定是过剩数,但确定不会是亏数(Erdős, Surányi and Guiduli. Topics in the Theory of Numbers p214. Springer 2003.)
  3. ^ Paul Erdős, Journal of the London Mathematical Society 9 (1934) 278–282.
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本原过剩数
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