281995

Appears in sequences

• Array T(n,k) = number of conjugacy classes of subgroups of index k in free group of rank n, read by antidiagonals.at n=47A057004
• Number of conjugacy classes of subgroups of index 3 in free group of rank n.at n=7A057009
• Wiener index of a benzenoid consisting of a double-step zig-zag chain of n hexagons (n >= 2, s = 2123; see the Gutman et al. reference).at n=35A193395