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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 56 |
| 5 | 552 |
| 6 | 7202 |
| 7 | 118456 |
| 8 | 2369922 |
| 9 | 56230544 |
| 10 | 1552048082 |
| 11 | 49080888144 |
| 12 | 1756527398738 |
| 13 | 70427165428648 |
| 14 | 3136819046716266 |
| 15 | 154090456510590632 |
| 16 | 8296738497931578818 |
| 17 | 487014208107376581984 |
| 18 | 31018372994440588508642 |
| 19 | 2134584265273475942046304 |
[1,1,2,8,56,552,7202,118456,2369922,56230544, 1552048082,49080888144,1756527398738, 70427165428648,3136819046716266, 154090456510590632,8296738497931578818, 487014208107376581984,31018372994440588508642, 2134584265273475942046304] |