A121445 - cp's OEIS frontend

A121445 Triangle read by rows: T(n,k) is the number of ternary trees with n edges and such that the first leaf in the preorder traversal is at level k (1<=k<=n). A ternary tree is a rooted tree in which each vertex has at most three children and each child of a vertex is designated as its left or middle or right child.

n	a(n)
1	3
2	3
3	9
4	10
5	18
6	27
7	42
8	69
9	81
10	81
11	198
12	312
13	351
14	324
15	243
16	1001
17	1540
18	1701
19	1566
20	1215
21	729
22	5304
23	8034
24	8784
25	8100
26	6480
27	4374
28	2187
29	29070
30	43554
31	47313
32	43713
33	35640
34	25515
35	15309
36	6561
37	163438
38	242896
39	262684
40	243108
41	200745
42	148716
43	96957

[3, 3, 9, 10, 18, 27, 42, 69, 81, 81, 198, 312, 351, 324, 243, 1001, 1540, 1701, 1566, 1215, 729, 5304, 8034, 8784, 8100, 6480, 4374, 2187, 29070, 43554, 47313, 43713, 35640, 25515, 15309, 6561, 163438, 242896, 262684, 243108, 200745, 148716, 96957]

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Table of values

List of values