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| n | a(n) |
|---|---|
| 4 | 15 |
| 5 | 185 |
| 6 | 1485 |
| 7 | 9905 |
| 8 | 59850 |
| 9 | 341082 |
| 10 | 1872990 |
| 11 | 10032990 |
| 12 | 52814025 |
| 13 | 274436305 |
| 14 | 1411449039 |
| 15 | 7195628895 |
| 16 | 36390053700 |
| 17 | 182622509860 |
| 18 | 909578754540 |
| 19 | 4496410556268 |
| 20 | 22062707386875 |
| 21 | 107464431586995 |
| 22 | 519700280676885 |
| 23 | 2495827315731365 |
| 24 | 11905791978208590 |
| 25 | 56429414876395550 |
[15,185,1485,9905,59850,341082,1872990,10032990, 52814025,274436305,1411449039,7195628895, 36390053700,182622509860,909578754540, 4496410556268,22062707386875,107464431586995, 519700280676885,2495827315731365, 11905791978208590,56429414876395550] |