n | a(n) |
---|---|
0 | 1 |
1 | 1 |
2 | 4 |
3 | 18 |
4 | 100 |
5 | 587 |
6 | 3660 |
7 | 23640 |
8 | 157076 |
9 | 1066281 |
10 | 7363620 |
11 | 51568732 |
12 | 365369868 |
13 | 2614235293 |
14 | 18862816112 |
15 | 137096744232 |
16 | 1002785827620 |
17 | 7376023180645 |
18 | 54525165453672 |
19 | 404858512190316 |
20 | 3018190533410664 |
21 | 22581907465905018 |
[1,1,4,18,100,587,3660,23640,157076,1066281, 7363620,51568732,365369868,2614235293,18862816112, 137096744232,1002785827620,7376023180645, 54525165453672,404858512190316,3018190533410664, 22581907465905018] |