This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A217075 #17 Jul 08 2025 14:35:17 %S A217075 2,14,19,31,44,53,71,82,117,127,131,145,177,197,203,241,258,261,276, %T A217075 283,293,320,325,379,387,388,406,413,461,462,470,486,491,534,549,569, %U A217075 582,612,618,639,696,706,723,746,765,767,774,796,802,877,878,903,923,981 %N A217075 Numbers k such that (k^31-1)/(k-1) is prime. %H A217075 Vincenzo Librandi, <a href="/A217075/b217075.txt">Table of n, a(n) for n = 1..1000</a> %t A217075 Select[Range[2, 1000], PrimeQ[(#^31 - 1)/(# - 1)] &] (* _T. D. Noe_, Sep 26 2012 *) %o A217075 (Magma) [n: n in [2..1000] |IsPrime((n^31 - 1) div (n - 1))]; // _Vincenzo Librandi_, Sep 28 2012 %o A217075 (PARI) is(n)=isprime((n^31-1)/(n-1)) \\ _Charles R Greathouse IV_, Feb 17 2017 %Y A217075 Cf. A002384, A049409, A100330, A162862, A217070-A217089. %K A217075 nonn,easy %O A217075 1,1 %A A217075 _Tim Johannes Ohrtmann_, Sep 26 2012 %E A217075 More terms from _T. D. Noe_, Sep 26 2012