n | a(n) |
---|---|
0 | 1 |
1 | 3 |
2 | 18 |
3 | 90 |
4 | 468 |
5 | 2412 |
6 | 12456 |
7 | 64296 |
8 | 331920 |
9 | 1713456 |
10 | 8845344 |
11 | 45662112 |
12 | 235720512 |
13 | 1216854720 |
14 | 6281741952 |
15 | 32428096128 |
16 | 167402836224 |
17 | 864179921664 |
18 | 4461136704000 |
19 | 23029626345984 |
20 | 118885325607936 |
21 | 613719060507648 |
[1,3,18,90,468,2412,12456,64296,331920,1713456, 8845344,45662112,235720512,1216854720,6281741952, 32428096128,167402836224,864179921664, 4461136704000,23029626345984,118885325607936, 613719060507648] |