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Revision difference : Redmond-Sun conjecture
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Conjecture. (Stephen Redmond \& Zhi-Wei Sun) Given positive integers $x$ and $y$, and exponents $a$ and $b$ (with all these numbers being greater than 1), if $x^a \neq y^b$, then between $x^a$ and $y^b$ there are always primes, with only the following ten exceptions: Conjecture. (Stephen Raymond \& Zhi-Wei Sun) Given positive integers $x$ and $y$, and exponents $a$ and $b$ (with all these numbers being greater than 1), if $x^a \neq y^b$, then between $x^a$ and $y^b$ there are always primes, with only the following ten exceptions:
\begin{enumerate} \begin{enumerate}
\item There are no primes between $2^3$ and $3^2$. \item There are no primes between $2^3$ and $3^2$.
\item There are no primes between $5^2$ and $3^3$. \item There are no primes between $5^2$ and $3^3$.
\item There are no primes between $2^5$ and $6^2$. \item There are no primes between $2^5$ and $6^2$.
\item There are no primes between $11^2$ and $5^3$. \item There are no primes between $11^2$ and $5^3$.
\item There are no primes between $3^7$ and $13^3$. \item There are no primes between $3^7$ and $13^3$.
\item There are no primes between $5^5$ and $56^2$. \item There are no primes between $5^5$ and $56^2$.
\item There are no primes between $181^2$ and $2^{15}$. \item There are no primes between $181^2$ and $2^{15}$.
\item There are no primes between $43^3$ and $282^2$. \item There are no primes between $43^3$ and $282^2$.
\item There are no primes between $46^3$ and $312^2$. \item There are no primes between $46^3$ and $312^2$.
\item There are no primes between $22434^2$ and $55^5$. \item There are no primes between $22434^2$ and $55^5$.
\end{enumerate} \end{enumerate}
See A116086 in Sloane's OEIS for a listing of the perfect powers beginning primeless ranges before the next perfect power. As of 2007, no further counterexamples have been found past $55^5$. See A116086 in Sloane's OEIS for a listing of the perfect powers beginning primeless ranges before the next perfect power. As of 2007, no further counteexamples have been found past $55^5$.