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A192583
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, 4, 6, and 8 are in S.
4
2, 4, 5, 6, 8, 11, 13, 17, 23, 31, 37, 41, 47, 53, 67, 79, 83, 89, 103, 107, 137, 139, 149, 167, 179, 223, 269, 283, 317, 359, 499, 557, 619, 643, 719, 823, 857, 1097, 1193, 1433, 1439, 1699, 1997, 2153, 2477, 2879, 3343, 4457, 6857, 7159, 8599, 12919, 41143
OFFSET
1,1
COMMENTS
See the discussion at A192580.
MATHEMATICA
start = {2, 4, 6, 8}; 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}]]]], # <
10000000 &]];
t = FixedPoint[b, start] (* A192583 *)
PrimePi[t] (* A192530 Nonprimes 4, 6, 8 are represented by "next prime down". *)
CROSSREFS
Cf. A192476.
Sequence in context: A284525 A353187 A099247 * A240064 A007192 A081354
KEYWORD
nonn,fini,full
AUTHOR
Clark Kimberling, Jul 04 2011
STATUS
approved