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 A267507 #29 Nov 24 2021 11:35:07
%S A267507 2,3,7,43,4903,168241543,5773040306503
%N A267507 Prime numbers n such that n-1 is squarefree and all prime divisors of n-1 other than 19 are in the sequence.
%t A267507 S[1] = {2, 19}; PR[S_] := Product[S[[i]], {i, Length[S]}];
%t A267507 S[m_] := S[m] = Union[S[m - 1], Select[Table[PR[Subsets[S[m - 1]] [[i]]] + 1, {i, 2^Length[S[m - 1]]}], PrimeQ]]; A267507 = Complement[S[7], {19}]
%t A267507 (* S[7]=S[8] ==> sequence is finite and full; _José María Grau Ribas_, Nov 22 2021 *)
%Y A267507 Cf. A267503, A267504, A267505, A267506, A267507.
%K A267507 nonn,fini,full
%O A267507 1,1
%A A267507 _José María Grau Ribas_, Jan 16 2016