Count the squares in 2020

For how many integers a a with 1 a 2020 1\leq a\leq2020 , a a a^a is a square? Bonus: Generalise this for 1 a n 1\leq a\leq n for some n N n\in \mathbb{N}


The answer is 1032.

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1 solution

Alexander Shannon
Jan 14, 2020

a a should be either even or an odd square integer, in order for a a a^a to be a square. There are 2020 2 = 1010 \frac{2020}{2}=1010 even integers and 2020 2 = 22 \frac{\lfloor \sqrt{2020}\rfloor}{2} = 22 odd squares, in the range 1 a 2020 1\leq a \leq 2020 , which add up to 1010 + 22 = 1032 1010+22=1032

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