A217246 Number of highly irregular connected graphs with n nodes.

1, 1, 0, 1, 0, 1, 0, 3, 3, 13, 21, 110, 474, 2545, 18696, 136749, 1447003, 18772435, 303050079, 6239596472

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], 2015-2016.

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: o--o--o--o

Crossrefs

Sequence in context: A363630 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