a(n) is the total number of down steps between the second and third up steps in all 2_1-Dyck paths of length 3*n. A 2_1-Dyck path is a lattice path with steps (1, 2), (1, -1) that starts and ends at y = 0 and stays above the line y = -1.
A334643
a(n) is the total number of down steps between the second and third up steps in all 2_1-Dyck paths of length 3*n. A 2_1-Dyck path is a lattice path with steps (1, 2), (1, -1) that starts and ends at y = 0 and stays above the line y = -1.
Terms
- a(0) =0a(1) =0a(2) =16a(3) =53a(4) =209a(5) =963a(6) =4816a(7) =25367a(8) =138531a(9) =777041a(10) =4449511a(11) =25901655a(12) =152818458a(13) =911755012a(14) =5491420104a(15) =33343242196a(16) =203881825163
External references
- oeis: A334643