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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 106 |
| 5 | 1060 |
| 6 | 21728 |
| 7 | 396648 |
| 8 | 10174764 |
| 9 | 267855264 |
| 10 | 8517836832 |
| 11 | 289596897480 |
| 12 | 11137252365600 |
| 13 | 461124747706896 |
| 14 | 20922578332613904 |
| 15 | 1018268757357253920 |
| 16 | 53372000211252229392 |
| 17 | 2981808910524462942720 |
| 18 | 177468245487057424475136 |
[1,0,2,6,106,1060,21728,396648,10174764,267855264, 8517836832,289596897480,11137252365600, 461124747706896,20922578332613904, 1018268757357253920,53372000211252229392, 2981808910524462942720,177468245487057424475136] |