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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 34 |
| 5 | 215 |
| 6 | 1682 |
| 7 | 15727 |
| 8 | 171274 |
| 9 | 2130275 |
| 10 | 29799722 |
| 11 | 463123747 |
| 12 | 7916886514 |
| 13 | 147635940335 |
| 14 | 2982555226562 |
| 15 | 64888568231767 |
| 16 | 1512552803481754 |
| 17 | 37608099684426395 |
| 18 | 993530210286226202 |
| 19 | 27791008680163167787 |
| 20 | 820556749933610580994 |
| 21 | 25502885614554196884455 |
[0,1,2,7,34,215,1682,15727,171274,2130275, 29799722,463123747,7916886514,147635940335, 2982555226562,64888568231767,1512552803481754, 37608099684426395,993530210286226202, 27791008680163167787,820556749933610580994, 25502885614554196884455] |