cp's OEIS Frontend

A192581 Monotonic ordering of set S generated by these rules: if x and y are in S and xy+1 is a prime, then xy+1 is in S, and 2 and 4 are in S.

%I A192581 #4 Mar 30 2012 18:57:35
%S A192581 2,4,5,11,17,23,47
%N A192581 Monotonic ordering of set S generated by these rules:  if x and y are in S and xy+1 is a prime, then xy+1 is in S, and 2 and 4 are in S.
%C A192581 See the discussion at A192580.  As sets, A192580 lies in A192581, which lies in A192582.
%t A192581 start = {2, 4}; primes = Table[Prime[n], {n, 1, 10000}];
%t A192581 f[x_, y_] := If[MemberQ[primes, x*y + 1], x*y + 1]
%t A192581 b[x_] :=
%t A192581   Block[{w = x},
%t A192581    Select[Union[
%t A192581      Flatten[AppendTo[w,
%t A192581        Table[f[w[[i]], w[[j]]], {i, 1, Length[w]}, {j, 1, i}]]]], # <
%t A192581       50000 &]];
%t A192581 t = FixedPoint[b, start]  (* A192581 *)
%Y A192581 Cf. A192476, A192580.
%K A192581 nonn,fini,full
%O A192581 1,1
%A A192581 _Clark Kimberling_, Jul 04 2011