A357856 Number of trails between two fixed distinct vertices in the complete undirected graph on n labeled vertices.

0, 1, 2, 15, 514, 106085, 317848626, 4238195548627, 2617666555119413330

Offset: 1

Author

Max Alekseyev, Oct 16 2022

Keywords

• nonn
• more
• walk

Comments

Trails are directed and pass through each (undirected) edge at most once in either of the two directions.

Crossrefs

Cf. A007082, A135388, A232545, A350028, A356366, A357855, A357857, A357885, A357886, A357887.

Formula

a(n) = Sum_{k = 0..n(n-1)/2} A357886(n,k).

Extensions

a(9) from Bert Dobbelaere, Oct 17 2022