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 A124198 #17 Sep 08 2022 08:45:28 %S A124198 2,6,10,16,18,20,22,26,30,32,36,42,46,48,50,52,62,68,70,76,82,92,96, %T A124198 102,108,110,116,120,126,128,130,136,146,148,158,160,168,170,172,176, %U A124198 178,182,186,198,200,202,206,220,222,228,230,236,238,246,248,258,262,278 %N A124198 Numbers k such that 21*k + 1 is prime. %H A124198 Harvey P. Dale, <a href="/A124198/b124198.txt">Table of n, a(n) for n = 1..1000</a> %e A124198 If k=148 then 21*k + 1 = 3109 (prime). %t A124198 Select[Range[300],PrimeQ[21#+1]&] (* _Harvey P. Dale_, Mar 08 2016 *) %o A124198 (Magma) [n: n in [0..300] | IsPrime(21*n + 1)] // _Vincenzo Librandi_, Mar 26 2010 %o A124198 (PARI) is(n)=isprime(21*n+1) \\ _Charles R Greathouse IV_, Jun 06 2017 %Y A124198 Cf. A024905, A124127. %K A124198 nonn,easy %O A124198 1,1 %A A124198 _Parthasarathy Nambi_, Dec 06 2006