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 A333721 #51 Jun 17 2020 17:15:43
%S A333721 1530,4260,25410,26040,78540,111720,174990,211050,214830,395430,
%T A333721 403260,409290,459690,487830,512820,711120,779790,910560,1023750,
%U A333721 1135950,1280370,1312350,1451520,1464810,1487070,1563510,1623360,1698060,1824330,1933680,2006340,2097480
%N A333721 Numbers k such that k + 1, 2k + 1, 3k + 1, 4k + 1, and 6k + 1 are all prime.
%C A333721 All terms are multiples of 6.
%C A333721 All terms are multiples of 30. - _Robert Israel_, Jun 17 2020
%H A333721 Robert Israel, <a href="/A333721/b333721.txt">Table of n, a(n) for n = 1..10000</a>
%H A333721 Pedro Caceres, <a href="/A333721/a333721.pdf">30 Ideas about Prime Numbers</a>
%e A333721 25410 is in the sequence because 25411, 50821, 76231, 101641, 152461 are all prime.
%p A333721 select(t -> andmap(isprime, [t+1,2*t+1,3*t+1,4*t+1,6*t+1]), [seq(i,i=30..3*10^6,30)]); # _Robert Israel_, Jun 17 2020
%o A333721 (PARI)
%o A333721 isok(m)={for(i=1, 6, if(i<>5&&!isprime(i*m+1), return(0))); 1}
%o A333721 { forstep(n=0, 3*10^6, 6, if(isok(n), print1(n, ", "))) } \\ _Andrew Howroyd_, May 04 2020
%Y A333721 Cf. A006093, A005097, A024892, A087370, A005098, A005099, A024898, A024899.
%K A333721 nonn
%O A333721 1,1
%A A333721 _Pedro Caceres_, May 04 2020