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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 15 |
| 3 | 92 |
| 4 | 624 |
| 5 | 4509 |
| 6 | 34033 |
| 7 | 265164 |
| 8 | 2116560 |
| 9 | 17219068 |
| 10 | 142252608 |
| 11 | 1190173956 |
| 12 | 10064038469 |
| 13 | 85873044573 |
| 14 | 738446318232 |
| 15 | 6393218956733 |
| 16 | 55680130965252 |
| 17 | 487488352916496 |
| 18 | 4288083926110045 |
| 19 | 37878037865662422 |
| 20 | 335859658273133355 |
| 21 | 2988274511990407436 |
[1,3,15,92,624,4509,34033,265164,2116560,17219068, 142252608,1190173956,10064038469,85873044573, 738446318232,6393218956733,55680130965252, 487488352916496,4288083926110045, 37878037865662422,335859658273133355, 2988274511990407436] |