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A194090
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The number of biconnected squaregraphs of perimeter 2*n.
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5
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OFFSET
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1,4
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COMMENTS
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The CWEB program squaregraph.w cited below relates a(n) to the number of certain partitions of {1,2,...,2*n} into n pairs.
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REFERENCES
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See A194088
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LINKS
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Table of n, a(n) for n=1..10.
Don Knuth, squaregraph.w (CWEB program).
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EXAMPLE
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For n=4 the a(4)=3 cases of perimeter 8 are the two trominoes and the square tetromino.
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PROG
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(CWEB) (see Knuth link).
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CROSSREFS
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A194088, A194089, A194091, A194092, A194093.
Sequence in context: A192212 A148918 A216541 * A020099 A182392 A005635
Adjacent sequences: A194087 A194088 A194089 * A194091 A194092 A194093
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KEYWORD
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nonn,hard,more
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AUTHOR
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Don Knuth, Aug 15 2011
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STATUS
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approved
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