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Find the sum of all positive integers which can be expressed as $\sqrt{7p^n+9}$ for some positive integer $n$ and some prime number $p$.

Official answer 49, my answer 10+11+24=45. Is it wrong ?

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    $\begingroup$ Indeed, $45\ne49$. $\endgroup$ – Yves Daoust Jan 28 '17 at 14:46
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    $\begingroup$ I think they have also added $\sqrt {7 (1)^n +9} =4$, but clearly $1$ is not prime. $\endgroup$ – Rohan Jan 28 '17 at 14:48
  • $\begingroup$ @ Rohan, I think so. Thank you both. $\endgroup$ – carat Jan 28 '17 at 15:46
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    $\begingroup$ I think, they knew that $p=1$ was not prime, and included $n=0$ (for some "non-negative integer", instead of "positive" integer). $\endgroup$ – Dietrich Burde Jan 28 '17 at 16:46
  • $\begingroup$ @Dietrich Burde, you're right. Thank you. $\endgroup$ – carat Jan 28 '17 at 18:01

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