I am wondering how I should interpret the notation that the Online Encyclopedia of Integer Sequences (OEIS) uses for finite groups.
An example is this sequence: A008795 In this specific case, what does the notation [2,n]+ = 22n mean?
Also, often these groups are mentioned because of their Molien series, that as far as I understand is the Hilbert series of the ring of invariants of a fixed representation. However, often the representation is not mentioned, so I guess these groups come with some natural representation of which the corresponding sequence is the Molien series. Is this correct?