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 A002642 M4606 N1131 #25 Oct 17 2023 08:19:14 %S A002642 9,29,35,42,48,113,120,126,152,185,204,224,237,243,276,302,308,321, %T A002642 341,386,399,419,432,477,503,510,516,542,549,588,633,659,666,705,731, %U A002642 770,776,783,789,815,848,854,887,906,932,945,965,978 %N A002642 Numbers k such that (k^2 + k + 1)/13 is prime. %C A002642 All terms are congruent to 3 or 9 (mod 13). [_Bruno Berselli_, Sep 26 2012] %D A002642 A. J. C. Cunningham, Binomial Factorisations, Vols. 1-9, Hodgson, London, 1923-1929; see Vol. 1, pp. 245-259. %D A002642 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). %D A002642 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A002642 Vincenzo Librandi, <a href="/A002642/b002642.txt">Table of n, a(n) for n = 1..1000</a> %H A002642 A. J. C. Cunningham, <a href="/A001912/a001912.pdf">Binomial Factorisations</a>, Vols. 1-9, Hodgson, London, 1923-1929. [Annotated scans of a few pages from Volumes 1 and 2] %t A002642 Select[Range[1000], PrimeQ[(#^2 + # + 1)/13]&] (* _Vincenzo Librandi_, Sep 25 2012 *) %o A002642 (PARI) forstep(n=9,1e4,[7,6],if(isprime((n^2+n+1)/13),print1(n", "))) \\ _Charles R Greathouse IV_, Sep 25 2012 %o A002642 (Magma) %o A002642 I:=[m: m in [1..1000] | m mod 13 in [3,9]]; %o A002642 [n: n in I | IsPrime( (n^2 + n + 1) div 13 )]; %o A002642 // _Bruno Berselli_, Sep 26 2012 %K A002642 nonn,easy %O A002642 1,1 %A A002642 _N. J. A. Sloane_