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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 9 |
| 3 | 48 |
| 4 | 286 |
| 5 | 1818 |
| 6 | 12086 |
| 7 | 82992 |
| 8 | 584079 |
| 9 | 4190738 |
| 10 | 30539814 |
| 11 | 225426240 |
| 12 | 1681904909 |
| 13 | 12663614266 |
| 14 | 96099303213 |
| 15 | 734250983952 |
| 16 | 5643749482600 |
| 17 | 43610375803722 |
| 18 | 338578974873523 |
| 19 | 2639771240159904 |
| 20 | 20659895819582337 |
[1,2,9,48,286,1818,12086,82992,584079,4190738, 30539814,225426240,1681904909,12663614266, 96099303213,734250983952,5643749482600, 43610375803722,338578974873523,2639771240159904, 20659895819582337] |