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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 10 |
| 3 | 72 |
| 4 | 670 |
| 5 | 7896 |
| 6 | 113572 |
| 7 | 1939028 |
| 8 | 38463550 |
| 9 | 869985586 |
| 10 | 22098989952 |
| 11 | 622728621984 |
| 12 | 19271496576612 |
| 13 | 649553583740576 |
| 14 | 23680212403186584 |
| 15 | 928276782505698920 |
| 16 | 38931911577966732814 |
| 17 | 1739307919812511213916 |
| 18 | 82457732209611432170734 |
[1,2,10,72,670,7896,113572,1939028,38463550, 869985586,22098989952,622728621984,19271496576612, 649553583740576,23680212403186584, 928276782505698920,38931911577966732814, 1739307919812511213916,82457732209611432170734] |