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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 0 |
| 6 | 1 |
| 7 | 1 |
| 8 | 5 |
| 9 | 4 |
| 10 | 19 |
| 11 | 26 |
| 12 | 163 |
| 13 | 445 |
| 14 | 2302 |
| 15 | 10798 |
| 16 | 63690 |
| 17 | 381883 |
| 18 | 2550827 |
| 19 | 17945643 |
[0,0,0,1,0,1,1,5,4,19,26,163,445,2302,10798,63690, 381883,2550827,17945643] |