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A192613 Monotonic ordering of set S generated by these rules:  if x and y are in S and x^2+2y^2 is a prime, then x^2+2y^2 is in S, and 1, 2, and 4 are in S. 3
1, 2, 3, 4, 11, 17, 19, 41, 139, 251, 307, 379, 587, 1699, 3371 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

See the discussions at A192476 and A192580.

LINKS

Table of n, a(n) for n=1..15.

MATHEMATICA

start = {1, 2, 4}; primes = Table[Prime[n], {n, 1, 20000}];

f[x_, y_] := If[MemberQ[primes, x^2 + 2 y^2], x^2 + 2 y^2]

b[x_] :=

  Block[{w = x},

   Select[Union[

     Flatten[AppendTo[w,

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

         Length[w]}]]]], # < 30000 &]];

t = FixedPoint[b, start] (* A192613 *)

CROSSREFS

Cf. A192612, A192476, A192580.

Sequence in context: A141704 A061919 A328883 * A002098 A301318 A297180

Adjacent sequences:  A192610 A192611 A192612 * A192614 A192615 A192616

KEYWORD

nonn,fini,full

AUTHOR

Clark Kimberling, Jul 05 2011

STATUS

approved

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Last modified September 27 16:11 EDT 2020. Contains 337383 sequences. (Running on oeis4.)