A258498 - cp's OEIS frontend

A258498 Number of words of length 2n 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 doublets into the initially empty word.

n	a(n)
0	1
1	1
2	3
3	15
4	105
5	933
6	9988
7	124449
8	1761287
9	27813479
10	483482018
11	9153385959
12	187129080977
13	4102129113670
14	95861136747795
15	2376234441556411
16	62216635372018209
17	1714347701138957189
18	49553280367466054768
19	1498300016807379304877
20	47270249397381096576643

[1, 1, 3, 15, 105, 933, 9988, 124449, 1761287, 27813479, 483482018, 9153385959, 187129080977, 4102129113670, 95861136747795, 2376234441556411, 62216635372018209, 1714347701138957189, 49553280367466054768, 1498300016807379304877, 47270249397381096576643]

cp's OEIS Frontend

A258498 Number of words of length 2n 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 doublets into the initially empty word.

Table of values

List of values