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Heath-Brown [Acta Math. 186(2001), 1-84] proved in 2001 that there are infinitely many primes of the form $x^3+2y^3$ with $x,y\in\mathbb Z^+=\{1,2,3,\ldots\}$.

In contrast, here I ask the following question.

Question 1. Are there infinitely many primes of the form $x^2+xy^2+y^3=x^2+(x+y)y^2$ with $x,y\in\mathbb Z^+$? Is it possible to provide a positive answer with a proof?

This question is motivated by my following conjecture (cf. http://oeis.org/A232174).

Conjecture 1. Any integer $n>1$ can be written as $x+y$ with $x,y\in\mathbb Z^+$ such that $x+ny$ and $x^2+ny^2$ are both prime.

This conjecture implies that Question 1 has a positive answer.

By a theorem of Heath-Brown and Moroz [Proc. London Math. Soc. 84(2002), 257-288], there are infinitely many primes of the form $x^3+(x+y)y^2$ with $x,y\in\mathbb Z^+$. Here I ask the following further question.

Question 2. Are there infinitely many primes of the form $p^3+(p+q)q^2$ with $p$ prime and $q\in\mathbb Z^+$?

This was motivated by my following conjecture (cf. http://oeis.org/A232186).

Conjecture 2. Any integer $n>2$ can be written as $p+q$ with $q\in\mathbb Z^+$ such that $p$ and $p^3+nq^2$ are both prime.

Conjecture 2 implies that Question 2 has a positive answer.

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    $\begingroup$ Heath-Brown and Moroz. $\endgroup$
    – Lucia
    Commented May 13, 2020 at 0:46
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    $\begingroup$ Thanks. By Heath-Brown and Moroz's result, there are infinitely many primes of the form $x^3+(x+y)y^2$. Now we focus on primes of the form $x^2+(x+y)y^2$. $\endgroup$ Commented May 13, 2020 at 1:03
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    $\begingroup$ It is possible to show that $x^2 + xy^2 + y^4$ takes on infinitely many prime values (and possibly with $y$ being restricted to be prime as well) by generalizing Friedlander-Iwaniec (and Heath-Brown/Li respectively), but these methods won’t work with $x^2 + xy^2 + y^3$. $\endgroup$ Commented May 13, 2020 at 1:18
  • $\begingroup$ I have extended the posting by adding Question 2 and Conjecture 2. $\endgroup$ Commented May 13, 2020 at 7:45

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