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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 22 |
| 4 | 194 |
| 5 | 2268 |
| 6 | 34272 |
| 7 | 624804 |
| 8 | 13432120 |
| 9 | 332078160 |
| 10 | 9286572624 |
| 11 | 289821031344 |
| 12 | 9985648515504 |
| 13 | 376489542984384 |
| 14 | 15418392593403360 |
| 15 | 681562973789926560 |
| 16 | 32345053760113660800 |
| 17 | 1640243700728870131200 |
| 18 | 88516191520113318169344 |
| 19 | 5064936155664187593030912 |
[1,2,4,22,194,2268,34272,624804,13432120, 332078160,9286572624,289821031344,9985648515504, 376489542984384,15418392593403360, 681562973789926560,32345053760113660800, 1640243700728870131200,88516191520113318169344, 5064936155664187593030912] |