Index of the closure of a triangle group Delta, associated with billiards in a regular n-gon, in the adelic group Gamma = SL_2(O), where O is the profinite completion of Z[zeta + zeta^{-1}] and zeta is the n-th root of unity.

A374898

Index of the closure of a triangle group Delta, associated with billiards in a regular n-gon, in the adelic group Gamma = SL_2(O), where O is the profinite completion of Z[zeta + zeta^{-1}] and zeta is the n-th root of unity.