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| n | a(n) |
|---|---|
| 0 | -1 |
| 1 | -1 |
| 2 | 2 |
| 3 | 14 |
| 4 | 62 |
| 5 | 317 |
| 6 | 1967 |
| 7 | 13544 |
| 8 | 98012 |
| 9 | 731273 |
| 10 | 5581682 |
| 11 | 43377617 |
| 12 | 342035204 |
| 13 | 2729286017 |
| 14 | 21996002729 |
| 15 | 178769985791 |
| 16 | 1463465010995 |
| 17 | 12055667829734 |
| 18 | 99858109234379 |
| 19 | 831150925169516 |
| 20 | 6947819513136614 |
| 21 | 58303331305857293 |
| 22 | 490961900646977570 |
[-1,-1,2,14,62,317,1967,13544,98012,731273, 5581682,43377617,342035204,2729286017,21996002729, 178769985791,1463465010995,12055667829734, 99858109234379,831150925169516,6947819513136614, 58303331305857293,490961900646977570] |