A321031 - cp's OEIS frontend

A321031 Number of words of length 3n such that the index set of occurring letters is {1, 2, ..., k}, all letters are introduced in ascending order, and the words can be built by repeatedly inserting triples into the initially empty word.

n	a(n)
0	1
1	1
2	4
3	31
4	351
5	5144
6	91816
7	1918578
8	45687682
9	1216354021
10	35689352250
11	1141323078031
12	39429988969021
13	1461049507764175
14	57720478019188989
15	2419008380691088543
16	107083662651332423339
17	4988596265684542112304
18	243781041304397011647766

[1, 1, 4, 31, 351, 5144, 91816, 1918578, 45687682, 1216354021, 35689352250, 1141323078031, 39429988969021, 1461049507764175, 57720478019188989, 2419008380691088543, 107083662651332423339, 4988596265684542112304, 243781041304397011647766]

cp's OEIS Frontend

A321031 Number of words of length 3n such that the index set of occurring letters is {1, 2, ..., k}, all letters are introduced in ascending order, and the words can be built by repeatedly inserting triples into the initially empty word.

Table of values

List of values