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OMCPLP 2016 Problem 5

  • Day 2

A numerical sequence is called lusophone if it satisfies the following three conditions: i) The first term of the sequence is number 11 . ii) To obtain the next term of the sequence we can multiply the previous term by a positive prime number ( 2,3,5,7,11,...2,3,5,7,11, ... ) or add 11 . (iii) The last term of the sequence is the number 20162016 . For example: 1→×1111→×61671→+1672→×320161\overset{{\times 11}}{\to}11 \overset{{\times 61}}{\to} 671 \overset{{+1}}{\to}672 \overset{{\times 3}}{\to}2016 How many Lusophone sequences exist in which (as in the example above) the add 11 operation was used exactly once and not multiplied twice by the same prime number?

Dataset text AI-MO AoPS. Quoted with source.

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Locator lusophon/2016/p5 · Tag 6BHRWFY5E8 · Edit this page on GitHub · Keys: j next, k previous