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A005047
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Minimal span of set of n elements with no 3-term arithmetic progression.
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12
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0, 1, 3, 4, 8, 10, 12, 13, 19, 23, 25, 29, 31, 35, 39, 40, 50, 53, 57, 62, 70, 73, 81, 83, 91, 94, 99, 103, 110, 113, 120, 121, 136, 144, 149, 156, 162, 164, 168, 173, 193, 203, 208
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OFFSET
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1,3
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COMMENTS
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Length of shortest ruler with n marks, with no mark halfway between two other marks. - Christian Häggström, Nov 19 2018
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REFERENCES
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R. K. Guy, Unsolved Problems in Number Theory, E10 (but beware of errors).
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LINKS
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FORMULA
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EXAMPLE
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Example for a(10) = 23: 0 1 4 6 10 15 17 18 22 23.
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CROSSREFS
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KEYWORD
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nonn,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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