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1985 AMC 12 Question 27

AMC12 · 1985 AMC 12

Question 27

Consider a sequence $x_1,$ $x_2,$ $x_3,$ $\ldots,$ defined by $$
\begin{aligned} x_1&=\sqrt[3]{3},\\ x_2&=(\sqrt[3]{3})^{\sqrt[3]{3}}. \end{aligned}
$$ and in general $$
x_n=(x_{n-1})^{\sqrt[3]{3}}
$$ for $n\gt1.$ What is the smallest value of $n$ for which $x_n$ is an integer?
  1. $2$
  2. $3$
  3. $4$
  4. $9$
  5. $27$