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| n | a(n) |
|---|---|
| 1 | 6 |
| 2 | 15 |
| 3 | 40 |
| 4 | 165 |
| 5 | 624 |
| 6 | 2635 |
| 7 | 11160 |
| 8 | 48915 |
| 9 | 217040 |
| 10 | 976887 |
| 11 | 4438920 |
| 12 | 20346485 |
| 13 | 93900240 |
| 14 | 435970995 |
| 15 | 2034505656 |
| 16 | 9536767665 |
| 17 | 44878791360 |
| 18 | 211927736135 |
| 19 | 1003867701480 |
| 20 | 4768372070757 |
| 21 | 22706531350480 |
| 22 | 108372083629275 |
[6,15,40,165,624,2635,11160,48915,217040,976887, 4438920,20346485,93900240,435970995,2034505656, 9536767665,44878791360,211927736135,1003867701480, 4768372070757,22706531350480,108372083629275] |