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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 1 |
| 6 | 4 |
| 7 | 25 |
| 8 | 136 |
| 9 | 772 |
| 10 | 4953 |
| 11 | 35340 |
| 12 | 288335 |
| 13 | 2632792 |
| 14 | 26726855 |
| 15 | 296550560 |
[0,0,0,0,1,4,25,136,772,4953,35340,288335,2632792, 26726855,296550560] |