| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 12 |
| 3 | 75 |
| 4 | 744 |
| 5 | 11181 |
| 6 | 242835 |
| 7 | 7330930 |
| 8 | 297801232 |
| 9 | 15839503630 |
| 10 | 1077837497949 |
| 11 | 92001213821228 |
| 12 | 9684980747377593 |
| 13 | 1239048275916503276 |
| 14 | 190191205778008667316 |
| 15 | 34634317805556075695994 |
[1,3,12,75,744,11181,242835,7330930,297801232, 15839503630,1077837497949,92001213821228, 9684980747377593,1239048275916503276, 190191205778008667316,34634317805556075695994] |