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2015 Paraguayan Mathematical Olympiad: Problem 1

Source:

October 4, 2015
algebra

Problem Statement

Alexa wrote the first 1616 numbers of a sequence: 1,2,2,3,4,4,5,6,6,7,8,8,9,10,10,11,1, 2, 2, 3, 4, 4, 5, 6, 6, 7, 8, 8, 9, 10, 10, 11, … Then she continued following the same pattern, until she had 20152015 numbers in total. What was the last number she wrote?