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A227358
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Length of shortest Golomb-like (for sums of triples) ruler with n marks.
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2
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OFFSET
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1,3
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COMMENTS
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a(n) is the least integer such that there is an n-element set of integers between 0 and a(n), the sums of triples (of not necessarily distinct elements) of which are distinct.
a(11) = 445 or a(11) < 440, but disproving the latter will take many cpu-years with the given program. - John Tromp, Aug 28 2013
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LINKS
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FORMULA
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EXAMPLE
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a(4) = 11 because 0-1-7-11 (0-4-10-11) and 0-1-8-11 (0-3-10-11) have all (6 choose 3)=20 distinct triple sums and there is no 0=b0<b1<b2<b3<11 with distinct triple sums.
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PROG
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See link.
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CROSSREFS
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KEYWORD
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nonn,hard,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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