Number of ternary trees with n internal nodes labeled 1 or 2; nodes labeled 1 have three linearly ordered children, but nodes labeled 2 have three children which are reversible (the first and third children may be transposed but the middle child must remain in place).

A391194

Number of ternary trees with n internal nodes labeled 1 or 2; nodes labeled 1 have three linearly ordered children, but nodes labeled 2 have three children which are reversible (the first and third children may be transposed but the middle child must remain in place).