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A307317
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Number of unlabeled connected leafless loopless multigraphs with n edges.
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3
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1, 0, 1, 2, 4, 9, 26, 68, 217, 718, 2553, 9574, 38005, 157306, 679682, 3047699, 14150278, 67844305, 335262807, 1704500229, 8902528600, 47704608478, 261960998230, 1472618327415, 8466681788462, 49743177379613, 298407523833717, 1826531247381194, 11399711132242500, 72500116125222893, 469578870456459042
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OFFSET
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0,4
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COMMENTS
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Connected multigraphs with no loops and no vertices of degree 1.
The initial terms were computed with Nauty.
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LINKS
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FORMULA
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Inverse Euler transform of A307316.
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EXAMPLE
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For n=3 the multigraphs (as sets of edges) are {(0,1),(0,1),(0,1)} and {(0,1),(0,2),(1,2)}.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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