A357856 - OEIS

%I #15 Oct 19 2022 07:14:06

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

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

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

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

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

%K nonn,more,walk

%O 1,3

%A _Max Alekseyev_, Oct 16 2022

%E a(9) from _Bert Dobbelaere_, Oct 17 2022