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A007417
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If n appears, 3n does not.
(Formerly M0954)
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6
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1, 2, 4, 5, 7, 8, 9, 10, 11, 13, 14, 16, 17, 18, 19, 20, 22, 23, 25, 26, 28, 29, 31, 32, 34, 35, 36, 37, 38, 40, 41, 43, 44, 45, 46, 47, 49, 50, 52, 53, 55, 56, 58, 59, 61, 62, 63, 64, 65, 67, 68, 70, 71, 72, 73
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| The characteristic function of this sequence is given by A014578. - DELEHAM Philippe (kolotoko(AT)wanadoo.fr), Mar 21 2004
Numbers n such that their ternary representation ends in even number of zeros . - DELEHAM Philippe (kolotoko(AT)wanadoo.fr), Mar 25 2004
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REFERENCES
| Aviezri S. Fraenkel, The vile, dopy, evil and odious game players, Discrete Math., to appear (2010).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..1000
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FORMULA
| Lim n -> infinity a(n)/n = 4/3 . - DELEHAM Philippe (kolotoko(AT)wanadoo.fr), Mar 21 2004
Partial sums of A092400. Indices of even numbers in A007949. Indices of odd numbers in A051064. a(n) = A092401(2n-1). - DELEHAM Philippe (kolotoko(AT)wanadoo.fr), Mar 29 2004
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EXAMPLE
| Contribution from Gary W. Adamson (qntmpkt(AT)yahoo.com), Mar 02 2010: (Start)
Given the following multiplication table: top row = "not multiples of 3"
left column = powers of 3; we get:
...
.1...2...4...5...7...8...10...11...13...
.3...6..12..15..21..24...30...33...39...
.9..18..36..45..63..72...90...99..114...
27..54.108..............................
81......................................
... If rows are labeled (1, 2, 3,...) then odd indexed rows are in the set; but
evens not. Examples: 9 is in the set since 3 is not, but 27 in row 4 can't be. (End)
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PROG
| (Haskell)
import Data.List (delete)
a007417 n = a007417_list !! (n-1)
a007417_list = s [1..] where
s (x:xs) = x : s (delete (3*x) xs)
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CROSSREFS
| Complement of A145204. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Oct 04 2008]
Sequence in context: A039137 A071807 A074232 * A039099 A035257 A175969
Adjacent sequences: A007414 A007415 A007416 * A007418 A007419 A007420
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KEYWORD
| easy,nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Simon Plouffe (simon.plouffe(AT)gmail.com)
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EXTENSIONS
| More terms from DELEHAM Philippe (kolotoko(AT)wanadoo.fr), Mar 29 2004
Typo corrected by Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Apr 15 2010
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