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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 0 |
| 4 | 8 |
| 5 | 34 |
| 6 | 92 |
| 7 | 180 |
| 8 | 1404 |
| 9 | 4288 |
| 10 | 29092 |
| 11 | 125384 |
| 12 | 859423 |
| 13 | 4746446 |
| 14 | 33970899 |
| 15 | 232212614 |
[0,1,0,8,34,92,180,1404,4288,29092,125384,859423, 4746446,33970899,232212614] |