The number of representations of $n$ by sum of 2 squares is known as sum of square function $r_2 (n)$. It is known that if prime factorization of $n$ is given as $$2^{a_0}p_1^{a_1}p_2^{a_2}\cdots q_1^{b_1}q_2^{b_2}\cdots$$ , where $p_i$s are primes of the form $4k+1$ and $q_i$s are primes of $4k+3$, then $r_2 (n)=0$ if any of $b_i$ is odd and $r_2 (n)=4(a_1+1)(a_2+1)\cdots$ if not.
However, I can't find any result that counts the number of representations of $n$ by sum of 2 coprime squares given its factorization. Can you find one?
By simple brute force and searching OEIS, I found that https://oeis.org/A000089 looks nearly identical to the function $r_{2, coprime}(n)$ I explained.
Can you prove or disprove $r_{2, coprime}(n) = A000089(n)$?