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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 20 |
| 3 | 392 |
| 4 | 11648 |
| 5 | 466112 |
| 6 | 23517824 |
| 7 | 1434077696 |
| 8 | 102618951680 |
| 9 | 8432793964544 |
| 10 | 782753794531328 |
| 11 | 81007725700038656 |
| 12 | 9249066952457584640 |
| 13 | 1154952975718091325440 |
| 14 | 156588371428134115868672 |
| 15 | 22908199202756436344963072 |
| 16 | 3597006040171205977538822144 |
[1,2,20,392,11648,466112,23517824,1434077696, 102618951680,8432793964544,782753794531328, 81007725700038656,9249066952457584640, 1154952975718091325440,156588371428134115868672, 22908199202756436344963072, 3597006040171205977538822144] |