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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A108687 Numbers of the form (9^i)*(11^j), with i, j >= 0. 12
1, 9, 11, 81, 99, 121, 729, 891, 1089, 1331, 6561, 8019, 9801, 11979, 14641, 59049, 72171, 88209, 107811, 131769, 161051, 531441, 649539, 793881, 970299, 1185921, 1449459, 1771561, 4782969, 5845851, 7144929, 8732691, 10673289, 13045131 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

MATHEMATICA

f[upto_]:=With[{max9=Floor[Log[9, upto]], max11=Floor[Log[11, upto]]}, Select[Union[Times@@{9^First[#], 11^Last[#]}&/@Tuples[{Range[0, max9], Range[0, max11]}]], #<=upto&]]; f[14000000]  (* Harvey P. Dale, Mar 11 2011 *)

PROG

(Haskell)

import Data.Set (singleton, deleteFindMin, insert)

a108687 n = a108687_list !! (n-1)

a108687_list = f $ singleton (1, 0, 0) where

   f s = y : f (insert (9 * y, i + 1, j) $ insert (11 * y, i, j + 1) s')

         where ((y, i, j), s') = deleteFindMin s

-- Reinhard Zumkeller, May 15 2015

CROSSREFS

Cf. A025633, A025634, A107788, A107764, A003596, A003597, A107988, A003598, A003599, A108090.

Sequence in context: A215831 A195941 A195992 * A038301 A277998 A289288

Adjacent sequences:  A108684 A108685 A108686 * A108688 A108689 A108690

KEYWORD

nonn

AUTHOR

Douglas Winston (douglas.winston(AT)srupc.com), Jun 17 2005

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 May 22 21:05 EDT 2019. Contains 323503 sequences. (Running on oeis4.)