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 A217072 #17 Jul 08 2025 15:01:06 %S A217072 2,10,11,12,14,19,24,40,45,46,48,65,66,67,75,85,90,103,105,117,119, %T A217072 137,147,164,167,179,181,205,220,235,242,253,254,263,268,277,303,315, %U A217072 332,337,366,369,370,389,399,404,424,431,446,449,480,481,506,509,521,523 %N A217072 Numbers k such that (k^19-1)/(k-1) is prime. %H A217072 Vincenzo Librandi, <a href="/A217072/b217072.txt">Table of n, a(n) for n = 1..1000</a> %t A217072 Select[Range[2, 1000], PrimeQ[(#^19 - 1)/(# - 1)] &] (* _T. D. Noe_, Sep 26 2012 *) %o A217072 (Magma) [n: n in [2..1000] |IsPrime((n^19 - 1) div (n - 1))]; // _Vincenzo Librandi_, Sep 28 2012 %o A217072 (PARI) is(n)=isprime((n^19-1)/(n-1)) \\ _Charles R Greathouse IV_, Feb 17 2017 %Y A217072 Cf. A002384, A049409, A100330, A162862, A217070-A217089. %K A217072 nonn,easy %O A217072 1,1 %A A217072 _Tim Johannes Ohrtmann_, Sep 26 2012 %E A217072 More terms from _T. D. Noe_, Sep 26 2012