n | a(n) |
---|---|
0 | 1 |
1 | 4 |
2 | 18 |
3 | 84 |
4 | 396 |
5 | 1872 |
6 | 8856 |
7 | 41904 |
8 | 198288 |
9 | 938304 |
10 | 4440096 |
11 | 21010752 |
12 | 99423936 |
13 | 470479104 |
14 | 2226331008 |
15 | 10535111424 |
16 | 49852682496 |
17 | 235905426432 |
18 | 1116316463616 |
19 | 5282466223104 |
20 | 24996898556928 |
21 | 118286594002944 |
[1,4,18,84,396,1872,8856,41904,198288,938304, 4440096,21010752,99423936,470479104,2226331008, 10535111424,49852682496,235905426432, 1116316463616,5282466223104,24996898556928, 118286594002944] |