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Search: id:A080342
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| A080342 |
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Number of weighings required to identify a single bad coin out of n coins, using a two-pan balance. |
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+0
2
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| 0, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5
(list; graph; listen)
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OFFSET
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1,4
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COMMENT
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It is known that there is exactly one bad coin, which is heavier than the others. No weights are used in the weighings.
0 appears once, 1 twice, 2 6 times, 3 18 times, 4 54 times, ...
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FORMULA
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a(n) = floor(L) - floor(2^(-f(L))) + 1, where L = log_3(n) and f() = fractional part.
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EXAMPLE
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a(1) = 0 since no weighings are needed - the coin is bad. a(2) = 1 since one weighing is needed.
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CROSSREFS
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Cf. A000244, A025192.
Adjacent sequences: A080339 A080340 A080341 this_sequence A080343 A080344 A080345
Sequence in context: A081326 A095139 A109038 this_sequence A081604 A123119 A099396
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KEYWORD
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nonn
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AUTHOR
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Artemario Tadeu Medeiros da Silva (artemario(AT)uol.com.br), Mar 19 2003
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EXTENSIONS
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More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 06 2003
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