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A007756
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Number of irreducible indecomposable spherical curves with n crossings (only ordinary double points), the circle is oriented, the sphere is not oriented (OU case).
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3
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0, 0, 1, 1, 2, 3, 11, 38, 156, 638, 2973, 13882, 67868, 338147, 1720303, 8905996, 46774728, 248918004, 1340083514, 7288922610, 40019870539, 221582395052, 1236358849827
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OFFSET
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1,5
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COMMENTS
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Old name was "Prime Gaussian (i.e. only ordinary double points) curves with n crossings."
Irreducible means not made disconnected by removal of a vertex (no nugatory crossings).
Indecomposable (or prime) means not made disconnected by cutting two distinct lines.
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LINKS
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PROG
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(C) See the J. Betrema C program in the Tait Curves link.
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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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Jean Betrema
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EXTENSIONS
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STATUS
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approved
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