A191128 Increasing sequence generated by these rules: a(1)=1, and if x is in a then 3x and 4x-1 are in a.

1, 3, 9, 11, 27, 33, 35, 43, 81, 99, 105, 107, 129, 131, 139, 171, 243, 297, 315, 321, 323, 387, 393, 395, 417, 419, 427, 513, 515, 523, 555, 683, 729, 891, 945, 963, 969, 971, 1161, 1179, 1185, 1187, 1251, 1257, 1259, 1281, 1283, 1291, 1539, 1545, 1547, 1569, 1571, 1579, 1665, 1667, 1675, 1707, 2049, 2051, 2059, 2091, 2187

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 = -1; f = 1; g = 9;
a = Union[Flatten[NestList[{h # + i, j # + k} &, f, g]]]  (* A191128 *)
b = a/3; c = (a + 1)/4; r = Range[1, 1500];
d = Intersection[b, r] (* A191180 *)
e = Intersection[c, r] (* A191181 *)
m = (a + 1)/2  (* divisibility property *)

Prog

(Haskell)
import Data.Set (singleton, deleteFindMin, insert)
a191128 n = a191128_list !! (n-1)
a191128_list = f $ singleton 1
   where f s = m : (f $ insert (3*m) $ insert (4*m-1) s')
             where (m, s') = deleteFindMin s
-- Reinhard Zumkeller, Jun 01 2011

Crossrefs

Cf. A191113, A191180, A191181.

Sequence in context: A060141 A107757 A191180 * A057261 A003597 A018705

Adjacent sequences: A191125 A191126 A191127 * A191129 A191130 A191131

Keyword

nonn

Author

Clark Kimberling, May 27 2011

Status

approved