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 A051644 #24 Feb 24 2025 02:02:57 %S A051644 13,19,31,43,67,79,103,139,223,283,367,439,499,607,619,643,787,823, %T A051644 907,1039,1087,1399,1447,1543,1579,1627,1663,1699,1759,1867,1879,1987, %U A051644 2083,2203,2239,2383,2659,2767,2803,3019,3343,3463,3559,3607,3643,3847,3919 %N A051644 Primes of the form 6*p + 1 where p is also prime. %C A051644 Analogous to A005385; can be called 6-safe primes. %H A051644 Amiram Eldar, <a href="/A051644/b051644.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Vincenzo Librandi) %F A051644 a(n) = 6*A007693(n) + 1. %e A051644 103 is in the sequence because both 17 and 6*17 + 1 = 103 are primes. %t A051644 Select[1 + 6Prime@Range[120], PrimeQ] (* _Ray Chandler_, Mar 14 2007 *) %o A051644 (PARI) isok(k) = isprime(k) && k % 6 == 1 && isprime((k-1)/6); \\ _Amiram Eldar_, Feb 24 2025 %Y A051644 Cf. A005384, A005385, A002476, A007693, A016921, A024899, A091178. %K A051644 nonn,easy %O A051644 1,1 %A A051644 _Labos Elemer_ %E A051644 Edited, corrected and extended by _Ray Chandler_, Mar 14 2007