TITLE: Prime coefficients in simultaneous equation. What are the integer solutions?
QUESTION [7 upvotes]: Let $p_1, p_2, p_3, p_4, p_5, p_6$ be consecutive primes in ascending order.
For what $p_1$ do $$p_1x+p_2y=p_3$$$$p_4x+p_5y=p_6$$ produce integer solutions $(x, y)$?
Example: $p_1=2, p_2=3, p_3=5, p_4=7, p_5=11, p_6=13$ give $x=16, y=-9$ which are integers.

Solving gives $$x=\frac{p_3p_5-p_2p_6}{p_1p_5-p_2p_4}\quad\text{and}\quad y=\frac{p_3-p_1x}{p_2}=\frac{p_1p_6-p_3p_4}{p_1p_5-p_2p_4}$$ However, I do not know how to find when $(p_1p_5-p_2p_4)|(p_3p_5-p_2p_6)$.
By trial and error, I have found the following solutions: $$p_1=2\implies(x,y)=(16,-9)$$$$p_1=5\implies(x,y)=(-9,-8)$$$$p_1=19\implies(x,y)=(-13,12)$$$$p_1=59\implies(x,y)=(-3,4)$$ I believe there are infinitely many $p_1$ that work.

REPLY [4 votes]: The infinitude of sextuplets of consecutive primes satisfying the given condition follows from some pretty strong well-known conjectures related to prime numbers. I will demonstrate it using Dickson's conjecture.
Consider the following six polynomials with integer coefficients:
$$\begin{array}{c}
p_1(n) := 210n + 59 \\
p_2(n) := 210n + 61 \\
p_3(n) := 210n + 67 \\
p_4(n) := 210n + 71 \\
p_5(n) := 210n + 73 \\
p_6(n) := 210n + 79 \\
\end{array}$$
Dickson's conjecture tells us that unless the product of these polynomials, $P(n)=\prod_i p_i(n)$ has a fixed divisor greater than $1$, there would be infinitely many integers $n$ for which all polynomials are simultaneously prime. The fixed divisor is a number which divides $P(n)$ for all integers $n$. This is easy to check in our case: $P(0)$ is a product of six primes and none of them divide $P(1)$. Thus, according to the conjecture, our polynomials should be simultaneously prime infinitely often.
It is also easy to see that $(x,y)=(-3,4)$ satisfies $$\begin{array}{c}
p_1(n)x+p_2(n)y = p_3(n) \\
p_4(n)x+p_5(n)y = p_6(n) \\
\end{array}$$
The only remaining bit we need to prove is that these six primes would be consecutive, regardless of the value of $n$. This is not too difficult to see, though: All the numbers between $59$ and $79$ other than those used as summands in one of the six polynomials share a factor common with $210=2\times 3\times 5\times 7$ and thus cannot be primes.
In summary: It is very likely there are infinitely many primes satisfying the given condition. If one could prove there are only finitely many of them, it would disprove a few strong conjectures. On the other hand, infinitude of primes of this specific type does not imply any of those well-known conjectures; it is possible all of them are false, yet the number of primes of this specific kind would still be infinite.