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| n | a(n) |
|---|---|
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 0 |
| 9 | 1 |
| 10 | 0 |
| 11 | 1 |
| 12 | 7 |
| 13 | 17 |
| 14 | 30 |
| 15 | 49 |
| 16 | 124 |
| 17 | 321 |
| 18 | 761 |
| 19 | 1721 |
| 20 | 3815 |
[0,0,0,0,0,1,0,1,7,17,30,49,124,321,761,1721,3815] |