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 A024897 #23 Sep 08 2022 08:44:48 %S A024897 3,5,11,15,17,21,27,29,35,39,45,47,53,69,71,75,77,81,83,87,89,95,99, %T A024897 101,113,119,123,131,141,143,147,153,161,165,167,171,183,185,201,203, %U A024897 207,209,213,221,225,245,249,251,255,257,263,279,281,285,287,291,297,299,309,311,315 %N A024897 Numbers k such that 5*k + 4 is prime. %H A024897 Vincenzo Librandi, <a href="/A024897/b024897.txt">Table of n, a(n) for n = 1..1000</a> %p A024897 A024897:=n->`if`(isprime(5*n+4), n, NULL): seq(A024897(n), n=1..500); # _Wesley Ivan Hurt_, Sep 07 2016 %t A024897 Select[Range[400], PrimeQ[5 # + 4]&] (* _Vincenzo Librandi_, Sep 25 2012 *) %o A024897 (Magma) [n: n in [1..1000] | IsPrime(5*n+4)] // _Vincenzo Librandi_, Nov 20 2010 %o A024897 (PARI) isok(n) = isprime(5*n+4) \\ _Michel Marcus_, Sep 07 2016 %Y A024897 Cf. A023218 (subsequence of primes). %K A024897 nonn,easy %O A024897 1,1 %A A024897 _Clark Kimberling_