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 A306719 #15 Mar 11 2019 09:36:25
%S A306719 2,4,8,10,20,22,28,30,50,58,64,72,80,82,88,108,114,134,148,172,190,
%T A306719 204,214,230,238,244,262,272,312,322,340,344,360,362,400,410,422,442,
%U A306719 458,498,514,552,554,568,594,610,620,640,688,712,730,750,758,784,792,814
%N A306719 Lexicographically earliest sequence containing 2 and all positive integers n such that the prime indices of n - 1 already belong to the sequence.
%C A306719 A self-describing sequence, similar to A304360.
%C A306719 A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
%F A306719 a(n) = A324699(n) + 1.
%t A306719 aQ[n_]:=Switch[n,0,False,2,True,_,And@@Cases[FactorInteger[n-1],{p_,k_}:>aQ[PrimePi[p]]]];
%t A306719 Select[Range[0,100],aQ]
%Y A306719 Prime indices of A324699.
%Y A306719 Cf. A000002, A000720, A001222, A001462, A007097, A055396, A061395, A079000, A079254, A109298, A112798, A276625, A277098, A304360.
%Y A306719 Cf. A324694, A324695, A324696, A324697, A324698, A324700, A324701, A324702, A324703, A324704, A324705.
%K A306719 nonn
%O A306719 1,1
%A A306719 _Gus Wiseman_, Mar 11 2019