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Timeline for Growth of $r_{2}(n)$

Current License: CC BY-SA 3.0

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Aug 19, 2018 at 23:23 comment added GH from MO If you like my answer, please accept it officially (so that it turns green). Thanks in advance!
Dec 23, 2014 at 17:00 comment added Noam D. Elkies Sorry, if I had references to hand I'd have given an answer rather than a comment. I see that meanwhile GH from MO supplied a more thorough answer with sources, so I refer you to his answer for further information.
Dec 23, 2014 at 12:13 answer added GH from MO timeline score: 18
Dec 23, 2014 at 6:55 answer added Charles timeline score: 3
Dec 23, 2014 at 6:50 comment added M.Souf Thank you Noam D. Elkies, could you give me the references for these statements.
Dec 23, 2014 at 6:37 comment added Noam D. Elkies It is known that $r_2(n)$ is usually zero: the number of $n<x$ such that $r_2(n) > 0$ is asymptotic to a multiple of $x\,\big/\sqrt{\log x} = o(x)$. But if $n$ is a product of $k$ distinct primes each congruent to $1 \bmod 4$ then $r_2(n) = 2^{k+2}$, which is $n^{o(1)}$ but grows much faster than polynomial in $\log n$ if we use the first $k$ primes in that congruence class.
Dec 23, 2014 at 6:00 history asked M.Souf CC BY-SA 3.0