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MathNet 2011 Question 29

Math Olympiad Vault · MathNet 2011

Question 29

Does there exist an increasing sequence of integers $0 = a_0 \lt a_1 \lt a_2 \lt \dots$, such that the following two conditions are satisfied:

1) every natural number can be written in the form $a_i + a_j$ for some (maybe equal) indices $i, j \ge 0$;

2) $a_n \gt \frac{n^2}{16}$ for all natural $n$?