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 A174813 a(n) = number whose product of digits equals a power of 3. 10
 1, 3, 9, 11, 13, 19, 31, 33, 39, 91, 93, 99, 111, 113, 119, 131, 133, 139, 191, 193, 199, 311, 313, 319, 331, 333, 339, 391, 393, 399, 911, 913, 919, 931, 933, 939, 991, 993, 999, 1111, 1113, 1119, 1131, 1133, 1139, 1191, 1193, 1199, 1311, 1313, 1319, 1331 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Equivalently, numbers whose decimal representation consists of digits from the set {1,3,9}. LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 EXAMPLE a(9)=39 is in the sequence because 3*9=3^3. MATHEMATICA Select[Range[2000], IntegerQ[Log[3, Times @@ (IntegerDigits[#])]] &] PROG (Haskell) a174813 n = a174813_list !! (n-1) a174813_list = f [1] where f ds = foldr (\d v -> 10 * v + d) 0 ds : f (s ds) s [] = [1]; s (9:ds) = 1 : s ds; s (d:ds) = 3*d : ds -- Reinhard Zumkeller, Jan 13 2014 CROSSREFS Cf. A028846, A061427. Sequence in context: A101620 A235583 A287333 * A116444 A215820 A065136 Adjacent sequences: A174810 A174811 A174812 * A174814 A174815 A174816 KEYWORD nonn,base AUTHOR Michel Lagneau, Dec 01 2010 STATUS approved

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Last modified December 9 02:18 EST 2023. Contains 367681 sequences. (Running on oeis4.)