| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 28 |
| 2 | 405 |
| 3 | 4032 |
| 4 | 31058 |
| 5 | 197288 |
| 6 | 1075697 |
| 7 | 5174180 |
| 8 | 22396787 |
| 9 | 88562288 |
| 10 | 323686749 |
| 11 | 1103799420 |
| 12 | 3538931886 |
| 13 | 10735761372 |
| 14 | 30981056614 |
| 15 | 85436083852 |
| 16 | 226032307036 |
| 17 | 575653531156 |
| 18 | 1415485760287 |
| 19 | 3369314791024 |
| 20 | 7781762472652 |
| 21 | 17474847498496 |
[1,28,405,4032,31058,197288,1075697,5174180, 22396787,88562288,323686749,1103799420,3538931886, 10735761372,30981056614,85436083852,226032307036, 575653531156,1415485760287,3369314791024, 7781762472652,17474847498496] |