54190080

Appears in sequences

• 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.at n=23A374898
• Number of Boolean intervals of rank 2 in the weak order of the Coxeter group of type C_n, for n >= 2.at n=6A380082