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 A023215 #40 Sep 08 2022 08:44:47 %S A023215 3,13,19,31,43,61,103,109,139,163,241,271,313,373,379,499,523,601,613, %T A023215 631,643,673,709,733,739,751,769,811,823,829,883,1021,1033,1051,1063, %U A023215 1069,1129,1171,1231,1249,1291,1381,1459,1483,1531,1549,1579,1621,1663 %N A023215 Primes p such that 4*p + 7 is also prime. %C A023215 Except for the first term, all terms are congruent to 1 (mod 6). - _John Cerkan_, Sep 07 2016 %H A023215 Vincenzo Librandi, <a href="/A023215/b023215.txt">Table of n, a(n) for n = 1..1000</a> %p A023215 A023215:=n->`if`(isprime(n) and isprime(4*n+7), n, NULL): seq(A023215(n), n=1..3*10^3); # _Wesley Ivan Hurt_, Sep 07 2016 %t A023215 Select[Prime[Range[300]],PrimeQ[4#+7]&] (* _Harvey P. Dale_, Jan 21 2011 *) %o A023215 (Magma) [n: n in PrimesUpTo(500) | IsPrime(4*n+7)]; // _Vincenzo Librandi_, Nov 19 2010 %Y A023215 Subsequence of primes of A089986. %K A023215 nonn,easy %O A023215 1,1 %A A023215 _David W. Wilson_