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 A051648 #16 Feb 24 2025 02:03:13
%S A051648 421,631,1051,1471,2311,2731,3571,4831,6091,9871,11131,12391,14071,
%T A051648 15331,17431,18691,21211,28771,29191,32971,34231,37591,38011,40111,
%U A051648 40531,46831,48091,52711,56911,58171,59011,65731,66571,72871,73291,74131,75391,84211,87991
%N A051648 Primes of form 210*p + 1 where p is a prime.
%C A051648 Generalization of A005385. Can be called 210-safe primes.
%C A051648 A002110(4)*p + 1 = 210*p + 1 (prime).
%H A051648 Amiram Eldar, <a href="/A051648/b051648.txt">Table of n, a(n) for n = 1..10000</a>
%F A051648 a(n) = 210 * A051647(n) + 1. - _Amiram Eldar_, Feb 24 2025
%e A051648 631 is in the sequence because 631 = 210*p + 1, where p=3.
%t A051648 Select[Table[210n+1,{n,Prime[Range[100]]}],PrimeQ] (* _Harvey P. Dale_, Dec 25 2016 *)
%o A051648 (PARI) isok(k) = isprime(k) && k % 210 == 1 && isprime((k-1)/210); \\ _Amiram Eldar_, Feb 24 2025
%Y A051648 Cf. A005384, A005385, A007693, A002110.
%K A051648 nonn,easy
%O A051648 1,1
%A A051648 _Labos Elemer_