A336544 Sum over all unlabeled graphs of order n, of the number of graphs obtainable by deletion of a single vertex in the graph.

1, 2, 6, 20, 90, 544, 5096, 79220, 2208158, 113737744, 10926144928

Offset

1,2

Comments

For a graph G with n vertices, consider deleting each vertex in turn (along with any associated edges). The resulting graphs will have n-1 vertices. Count the distinct graphs reached. This sequence gives the sum of this count over all graphs with n vertices.

Links

Table of n, a(n) for n=1..11.

Sean A. Irvine, Illustration of initial terms

Sean A. Irvine, Java program (github)

Crossrefs

Cf. A336545 (connected graphs).

Sequence in context: A079468 A124382 A318813 * A000666 A180890 A027321

Adjacent sequences: A336541 A336542 A336543 * A336545 A336546 A336547

Keyword

nonn,more

Author

Sean A. Irvine, Jul 25 2020

Status

approved