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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 0 |
| 4 | 3 |
| 5 | 3 |
| 6 | 18 |
| 7 | 39 |
| 8 | 157 |
| 9 | 459 |
| 10 | 1668 |
| 11 | 5503 |
| 12 | 19638 |
| 13 | 68325 |
| 14 | 245144 |
| 15 | 876438 |
| 16 | 3177651 |
| 17 | 11549939 |
| 18 | 42307920 |
| 19 | 155555733 |
| 20 | 574881920 |
| 21 | 2132231076 |
| 22 | 7938771624 |
| 23 | 29651189637 |
| 24 | 111086480106 |
| 25 | 417305224917 |
| 26 | 1571633677078 |
| 27 | 5932720163529 |
| 28 | 22443721850064 |
| 29 | 85075094996719 |
| 30 | 323086777251300 |
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