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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. 2
2, 4, 5, 11, 17, 23, 47 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

See the discussion at A192580.  As sets, A192580 lies in A192581, which lies in A192582.

LINKS

Table of n, a(n) for n=1..7.

MATHEMATICA

start = {2, 4}; primes = Table[Prime[n], {n, 1, 10000}];

f[x_, y_] := If[MemberQ[primes, x*y + 1], x*y + 1]

b[x_] :=

  Block[{w = x},

   Select[Union[

     Flatten[AppendTo[w,

       Table[f[w[[i]], w[[j]]], {i, 1, Length[w]}, {j, 1, i}]]]], # <

      50000 &]];

t = FixedPoint[b, start]  (* A192581 *)

CROSSREFS

Cf. A192476, A192580.

Sequence in context: A089416 A056817 A352255 * A095023 A049913 A223220

Adjacent sequences:  A192578 A192579 A192580 * A192582 A192583 A192584

KEYWORD

nonn,fini,full

AUTHOR

Clark Kimberling, Jul 04 2011

STATUS

approved

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Last modified August 9 21:08 EDT 2022. Contains 356026 sequences. (Running on oeis4.)