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A217246
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Number of highly irregular connected graphs with n nodes.
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0
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1, 1, 0, 1, 0, 1, 0, 3, 3, 13, 21, 110, 474, 2545, 18696, 136749, 1447003, 18772435, 303050079, 6239596472
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OFFSET
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1,8
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COMMENTS
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A connected graph is highly irregular if the neighbors of each vertex have distinct degrees. Such graphs exist on all orders except 3, 5 and 7. [from the McKay link]
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LINKS
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Table of n, a(n) for n=1..20.
Avraham Itzhakov and Michael Codish, Breaking Symmetries in Graph Search with Canonizing Sets, arXiv:1511.08205 [cs.AI], 2015-2016.
Brendan McKay, Combinatorial Data (on graphs); see bottom of page.
Eric Weisstein's World of Mathematics, Highly Irregular Graph
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EXAMPLE
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a(4) = 1, the only such graph is the linear graph: o--o--o--o
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CROSSREFS
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Sequence in context: A209390 A095336 A072552 * A186743 A219314 A288146
Adjacent sequences: A217243 A217244 A217245 * A217247 A217248 A217249
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KEYWORD
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more,nonn
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AUTHOR
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Joerg Arndt, Mar 16 2013
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EXTENSIONS
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a(16)-a(19) from Michael Codish, Dec 01 2015
a(20) from Michael Codish, Jan 17 2016
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STATUS
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approved
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