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 A051646 #14 Feb 24 2025 02:03:06 %S A051646 61,151,211,331,571,691,1231,1291,1831,2011,2131,2371,2671,3271,3391, %T A051646 3931,4111,5011,5431,5791,6691,6871,6991,8311,8431,9391,9511,9931, %U A051646 10111,10771,11491,13171,13291,13711,13831,14011,14731,15091,15271,16231,16411,17791,17971 %N A051646 Primes of the form 30*p + 1 where p is also prime. %C A051646 Analogous to A005385, safe primes. Can be called 30-safe primes. %H A051646 Amiram Eldar, <a href="/A051646/b051646.txt">Table of n, a(n) for n = 1..10000</a> %F A051646 a(n) = A128470(A051645(n)) = 30 * A051645(n) + 1. - _Amiram Eldar_, Feb 24 2025 %e A051646 61 is in the sequence because both 2 and 30*2 + 1 = 61 are primes. %t A051646 Select[30 * Prime[Range[120]] + 1, PrimeQ] (* _Amiram Eldar_, Feb 24 2025 *) %o A051646 (PARI) isok(k) = isprime(k) && k % 30 == 1 && isprime((k-1)/30); \\ _Amiram Eldar_, Feb 24 2025 %Y A051646 Cf. A005384, A005385, A007693, A051645, A128470. %K A051646 nonn,easy %O A051646 1,1 %A A051646 _Labos Elemer_