1,2

See the discussions at A192476 and A192580.

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

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 *)

Cf. A192612, A192476, A192580.

Sequence in context: A141704 A061919 A328883 * A002098 A301318 A297180

Adjacent sequences: A192610 A192611 A192612 * A192614 A192615 A192616

nonn,fini,full

Clark Kimberling, Jul 05 2011

approved