A191131 Increasing sequence generated by these rules: a(1)=1, and if x is in a then 3x and 4x+3 are in a.

1, 3, 7, 9, 15, 21, 27, 31, 39, 45, 63, 81, 87, 93, 111, 117, 127, 135, 159, 183, 189, 243, 255, 261, 279, 327, 333, 351, 375, 381, 405, 447, 471, 477, 511, 543, 549, 567, 639, 729, 735, 759, 765, 783, 837, 975, 981, 999, 1023, 1047, 1053, 1119, 1125, 1143, 1215, 1311, 1335, 1341, 1407, 1413, 1431, 1503, 1527, 1533, 1623

Offset

1,2

Comments

See A191113.

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Mathematica

h = 3; i = 0; j = 4; k = 3; f = 1; g = 9;
a = Union[Flatten[NestList[{h # + i, j # + k} &, f, g]]]   (* A191131 *)
b = a/3; c = (a - 3)/4; r = Range[1, 1500];
d = Intersection[b, r] (* A191186 *)
e = Intersection[c, r] (* A191187 *)

Prog

(Haskell)
import Data.Set (singleton, deleteFindMin, insert)
a191131 n = a191131_list !! (n-1)
a191131_list = f $ singleton 1
   where f s = m : (f $ insert (3*m) $ insert (4*m+3) s')
             where (m, s') = deleteFindMin s
-- Reinhard Zumkeller, Jun 01 2011

Crossrefs

Cf. A191113, A191186, A191187.

Note that A191131, A261524, A261871, and A282572 are very similar and easily confused with each other.

Sequence in context: A070993 A261524 A261871 * A282572 A299642 A128539

Adjacent sequences: A191128 A191129 A191130 * A191132 A191133 A191134

Keyword

nonn

Author

Clark Kimberling, May 27 2011

Status

approved