Comments to Generalized Chebyshev polynomial P₂₃

The interest to the trees M23a and M23b is due to the fact that they are the only (up to symmetry) trees edge rotation group of which is Matieu group M₂₃. This was proved by

N.M.Adrianov, Yu.Yu.Kochetkov, A.D.Suvorov and G.B.Shabat

Matieu groups and plane trees (in Russian)

Fundamental'naya i prikladnaya matematika, 1(2):377-384, 1995;

correction: ibid, 2(1):317, 1996