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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 3 |
| 6 | 12 |
| 7 | 49 |
| 8 | 482 |
| 9 | 6380 |
| 10 | 135252 |
| 11 | 3939509 |
| 12 | 166800470 |
| 13 | 9739584172 |
| 14 | 818717312364 |
| 15 | 95353226103276 |
[0,0,1,2,3,12,49,482,6380,135252,3939509, 166800470,9739584172,818717312364,95353226103276] |