2019 CIME I Problems/Problem 9

Let $\text{N}$ denote the number of strictly increasing sequences of positive integers $a_1,a_2,\cdots, a_{19}$ satisfying the following two rules$:$

  • $a_1=1$ and $a_{19}=361,$
  • for any $i \neq j,$ if $b_{ij}$ is the $(i \cdot j)^{\text{th}}$ number not in the sequence$,$ then $(a_i-b_{ij})(a_j-b_{ij})<0.$

Find the largest positive integer $k$ such that $2^k$ divides $\text{N}.$

Solution 1

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See also

2019 CIME I (ProblemsAnswer KeyResources)
Preceded by
Problem 8
Followed by
Problem 10
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
All CIME Problems and Solutions

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