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Half Integers

Author: mathforces
Problem has been solved: 2 times

Русский язык | English Language



Let $ X_n $ be the set of points $(\frac{a}{2}, \frac{b}{2})$ such that $ |a| \leq b \leq 2n$, where $ a $ and $ b $ are odd integers. Let $ K_n $ be the number of graphs $ G $ with vertices at points $ X_n $ such that in the graph $ G $:
  • no cycles
  • the length of any edge is $ 1 $
  • for any path $ P = (p_1, ..., p_m) $ of the graph $ G $, at least one of the points $ p_1 $ and $ p_m $ has the smallest value of the $ y $ -coordinate among the points of the path $ P $. Moreover, it is possible that several points have the smallest value of the $ y $ -coordinate.
Find the hundredth smallest positive integer number $ t $ such that $ K_{3t} $ has the last digit 4.





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