| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 48 |
| 2 | 1224 |
| 3 | 21952 |
| 4 | 309876 |
| 5 | 3657312 |
| 6 | 37468928 |
| 7 | 341773440 |
| 8 | 2826752418 |
| 9 | 21491641808 |
| 10 | 151810235136 |
| 11 | 1004753937600 |
| 12 | 6273891838360 |
| 13 | 37171410206112 |
| 14 | 209969121051648 |
| 15 | 1135389617917568 |
| 16 | 5897908848093087 |
| 17 | 29521227582821520 |
| 18 | 142760699405228800 |
[1,48,1224,21952,309876,3657312,37468928, 341773440,2826752418,21491641808,151810235136, 1004753937600,6273891838360,37171410206112, 209969121051648,1135389617917568,5897908848093087, 29521227582821520,142760699405228800] |