How many are non isomorphic tournaments (directed clique) with $n=5$ vertices?
I'm not sure how to understand isomorphism here. This problem was in the set of problems on Burnside's lemma but it's different than the rest, I think. Normally I was asked to count the number of significantly different colorings of necklace or chessboard which was very nice and the group for Burnside's lemma was given explicit - simply all rotations. But here I don't know what is the group, how to approach this.
Is it very difficult to solve this in general - for $n\in\mathbb{N}$?
Will it be useful here the term: graph automorphism? How to understand it? Because I have it in the next problem.