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Sep 4, 2018 at 15:21 comment added Mike Bennett One should be able to handle the more general equation $2^x-3z^y=5$ by appealing to lower bounds for linear forms in 2-adic logs to bound $x$ and $y$ and then using Frey curves ( a la Kraus) to knock off the remaining values of $y$ (likely one would have to do the cases where $2$ or $3$ divide $y$ separately via integral points on elliptic curve arguments or something similar). The most obvious couple of Frey curves give you congruences to forms of level $30$. The details shouldn't be too bad, but I'm not sure my claim follows explicitly from anything currently in the literature.
Sep 4, 2018 at 3:18 comment added GH from MO @MikeBennett: Very interesting. Can you give some details or references for your claim?
Sep 3, 2018 at 22:34 comment added Mike Bennett One can show that there are only two solutions with $y > 1$ (corresponding to $x=5$ and $x=9$), for arbitrary $p$. Presumably, there are infinitely many $p$ of the shape $(2^x-5)/3$.
Sep 2, 2018 at 7:47 history edited GH from MO CC BY-SA 4.0
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Sep 2, 2018 at 5:55 comment added KConrad The book you mention did not have Lang as a co-author.
Sep 2, 2018 at 5:48 vote accept qrilove
Sep 2, 2018 at 2:46 history edited GH from MO CC BY-SA 4.0
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Sep 2, 2018 at 2:26 history edited GH from MO CC BY-SA 4.0
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Sep 2, 2018 at 2:20 history edited GH from MO CC BY-SA 4.0
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Sep 2, 2018 at 2:05 history edited GH from MO CC BY-SA 4.0
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Sep 2, 2018 at 1:57 history answered GH from MO CC BY-SA 4.0