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A052445
Number of simple unlabeled n-node graphs of connectivity 4.
10
0, 0, 0, 0, 1, 3, 21, 345, 13429, 1109105, 162318088, 39460518399
OFFSET
1,6
LINKS
Brendan McKay, confusion over k-connected graphs, posting to Sequence Fans Mailing List, Jul 08 2015.
Eric Weisstein's World of Mathematics, k-Connected Graph
Eric Weisstein's World of Mathematics, Vertex Connectivity
FORMULA
a(n) = A086216(n) - A086217(n). - Andrey Zabolotskiy, Nov 20 2017
EXAMPLE
The a(6) = 3 exactly-4-connected 6-node graphs are the complete graph K_6 with 1, 2, or 3 non-adjacent edges removed.
CROSSREFS
KEYWORD
nonn,more,hard
EXTENSIONS
Partially edited by N. J. A. Sloane, Jul 08 2015 at the suggestion of Brendan McKay
a(8)-a(11) copied from A259862 by Andrey Zabolotskiy, Nov 20 2017
a(4)-a(5) corrected by Andrew Howroyd, Aug 28 2019
a(12) from Sean A. Irvine, Dec 12 2021
STATUS
approved