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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 1 |
| 5 | 7 |
| 6 | 33 |
| 7 | 139 |
| 8 | 566 |
| 9 | 2279 |
| 10 | 9132 |
| 11 | 36488 |
| 12 | 145500 |
| 13 | 579318 |
[0,0,0,1,1,7,33,139,566,2279,9132,36488,145500, 579318] |