Putnam 2015 B2
- Session B
Given a list of the positive integers , take the first three numbers and their sum and cross all four numbers off the list. Repeat with the three smallest remaining numbers and their sum . Continue in this way, crossing off the three smallest remaining numbers and their sum, and consider the sequence of sums produced: . Prove or disprove that there is some number in the sequence whose base 10 representation ends with .
Curated text Kedlaya Putnam archive. Quoted with source.
Solutions
Human solution Solution 1 by Manjul Bhargava, Kiran Kedlaya and Lenny Ng
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