

A217246


Number of highly irregular connected graphs with n nodes.


0



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

1,8


COMMENTS

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]


LINKS

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], 20152016.
Brendan McKay, Combinatorial Data (on graphs); see bottom of page.
Eric Weisstein's World of Mathematics, Highly Irregular Graph


EXAMPLE

a(4) = 1, the only such graph is the linear graph: oooo


CROSSREFS

Sequence in context: A209390 A095336 A072552 * A186743 A219314 A288146
Adjacent sequences: A217243 A217244 A217245 * A217247 A217248 A217249


KEYWORD

more,nonn


AUTHOR

Joerg Arndt, Mar 16 2013


EXTENSIONS

a(16)a(19) from Michael Codish, Dec 01 2015
a(20) from Michael Codish, Jan 17 2016


STATUS

approved



