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A105974
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(A001035(n) - 1)/2 where A001035 is the number of partially ordered sets ("posets") with n labeled elements.
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0
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0, 0, 1, 9, 109, 2115, 65011, 3064929, 215861689, 22255521255, 3305532624391, 698140838552949, 207432475527926749, 85925364190793529675, 49242162128564103516091, 38783585510220344176524969
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OFFSET
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0,4
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COMMENTS
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Conjectures: a(n) is (pre)periodic modulo m for all m, the lengths of the ending periods being given by 2*A000010(m) if m is a power of 2 and A000010(m) otherwise. A000010 is Euler's totient function.
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LINKS
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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