login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A191131 Increasing sequence generated by these rules:  a(1)=1, and if x is in a then 3x and 4x+3 are in a. 9
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 (list; graph; refs; listen; history; text; internal format)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified February 23 12:35 EST 2019. Contains 320431 sequences. (Running on oeis4.)