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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 20 |
| 4 | 231 |
| 5 | 3864 |
| 6 | 85360 |
| 7 | 2353546 |
| 8 | 77963599 |
| 9 | 3019479344 |
| 10 | 133966276692 |
| 11 | 6702399275538 |
| 12 | 373406941221160 |
| 13 | 22930441709648290 |
| 14 | 1539004344848618466 |
| 15 | 112089683771614695478 |
| 16 | 8805334896381292460191 |
| 17 | 742162775145283382779168 |
| 18 | 66809386370870410069346476 |
[1,1,3,20,231,3864,85360,2353546,77963599, 3019479344,133966276692,6702399275538, 373406941221160,22930441709648290, 1539004344848618466,112089683771614695478, 8805334896381292460191,742162775145283382779168, 66809386370870410069346476] |