| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 6 |
| 5 | 8 |
| 6 | 23 |
| 7 | 24 |
| 8 | 1804 |
| 9 | 1968 |
| 10 | 8375 |
| 11 | 53750 |
| 12 | 243864 |
| 13 | 639324 |
| 14 | 41381620 |
| 15 | 102621343 |
| 16 | 7802708736 |
| 17 | 7802708736 |
| 18 | 178874468615 |
| 19 | 1133934949368 |
[1,1,4,6,8,23,24,1804,1968,8375,53750,243864, 639324,41381620,102621343,7802708736,7802708736, 178874468615,1133934949368] |