a(n) is the total number of down steps between the 2nd and 3rd up steps in all 2-Dyck paths of length 3*n. A 2-Dyck path is a nonnegative lattice path with steps (1, 2), (1, -1) that starts and ends at y = 0.
A334640
a(n) is the total number of down steps between the 2nd and 3rd up steps in all 2-Dyck paths of length 3*n. A 2-Dyck path is a nonnegative lattice path with steps (1, 2), (1, -1) that starts and ends at y = 0.
Terms
- a(0) =0a(1) =0a(2) =9a(3) =19a(4) =72a(5) =324a(6) =1595a(7) =8307a(8) =44982a(9) =250648a(10) =1427679a(11) =8274825a(12) =48644310a(13) =289334160a(14) =1738043892a(15) =10529070020a(16) =64252519830a(17) =394601627376
External references
- oeis: A334640