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| n | a(n) |
|---|---|
| 3 | 0 |
| 4 | 0 |
| 5 | 2 |
| 6 | 8 |
| 7 | 6 |
| 8 | 16 |
| 9 | 58 |
| 10 | 120 |
| 11 | 252 |
| 12 | 670 |
| 13 | 1618 |
| 14 | 3754 |
| 15 | 9522 |
| 16 | 23886 |
| 17 | 59622 |
| 18 | 151875 |
| 19 | 392938 |
| 20 | 1014709 |
| 21 | 2648440 |
| 22 | 6966849 |
| 23 | 18374138 |
| 24 | 48654893 |
| 25 | 129490838 |
| 26 | 345287097 |
| 27 | 922517576 |
| 28 | 2471493256 |
| 29 | 6633768512 |
| 30 | 17829837307 |
| 31 | 48003235776 |
[0,0,2,8,6,16,58,120,252,670,1618,3754,9522,23886, 59622,151875,392938,1014709,2648440,6966849, 18374138,48654893,129490838,345287097,922517576, 2471493256,6633768512,17829837307,48003235776] |