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Search: id:A068979
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| A068979 |
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Number of elements of rank n in the free lattice on three generators. |
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+0
1
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OFFSET
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1,1
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COMMENT
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The rank of a lattice term is the number of occurrences of variables in that term. The rank of an element is the minimum rank of a term representing that element.
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EXAMPLE
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a(2) = 6 because the 6 elements of rank 2 are x + y, x + z, y + z, xy, xz, and yz.
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CROSSREFS
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Sequence in context: A039567 A032912 A123208 this_sequence A101060 A038064 A093899
Adjacent sequences: A068976 A068977 A068978 this_sequence A068980 A068981 A068982
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KEYWORD
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more,nonn
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AUTHOR
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David Wasserman (dwasserm(AT)earthlink.net), Mar 31 2002
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