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HMMT 二月 2008 · GEN1 赛 · 第 8 题

HMMT February 2008 — GEN1 Round — Problem 8

专题
Discrete Math / 离散数学
难度
L3
来源
HMMT

题目详情

  1. [ 5 ] Let S be the smallest subset of the integers with the property that 0 ∈ S and for any x ∈ S , we have 3 x ∈ S and 3 x + 1 ∈ S . Determine the number of positive integers in S less than 2008.
解析
  1. [ 5 ] Let S be the smallest subset of the integers with the property that 0 ∈ S and for any x ∈ S , we have 3 x ∈ S and 3 x + 1 ∈ S . Determine the number of positive integers in S less than 2008. Answer: 127 Same as Combinatorics Problem 5.