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 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

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