n | a(n) |
---|---|
1 | 0 |
2 | 0 |
3 | 2 |
4 | 9 |
5 | 30 |
6 | 89 |
7 | 258 |
8 | 720 |
9 | 2016 |
10 | 5583 |
11 | 15546 |
12 | 43215 |
13 | 120750 |
14 | 338001 |
15 | 950030 |
16 | 2677770 |
17 | 7573350 |
18 | 21478632 |
19 | 61088874 |
20 | 174179133 |
21 | 497812378 |
22 | 1425832077 |
23 | 4092087522 |
24 | 11765778330 |
25 | 33887517840 |
26 | 97756266615 |
27 | 282414622728 |
28 | 816999371955 |
29 | 2366509198350 |
30 | 6862929885407 |
[0,0,2,9,30,89,258,720,2016,5583,15546,43215, 120750,338001,950030,2677770,7573350,21478632, 61088874,174179133,497812378,1425832077, 4092087522,11765778330,33887517840,97756266615, 282414622728,816999371955,2366509198350, 6862929885407] |