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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 9 |
| 3 | 77 |
| 4 | 657 |
| 5 | 5605 |
| 6 | 47817 |
| 7 | 407933 |
| 8 | 3480129 |
| 9 | 29689429 |
| 10 | 253284345 |
| 11 | 2160801389 |
| 12 | 18434075121 |
| 13 | 157263470533 |
| 14 | 1341634934313 |
| 15 | 11445660526685 |
| 16 | 97644405002913 |
| 17 | 833017002919477 |
| 18 | 7106575406263641 |
| 19 | 60627110644694861 |
| 20 | 517217694177199185 |
| 21 | 4412450805016013221 |
[0,1,9,77,657,5605,47817,407933,3480129,29689429, 253284345,2160801389,18434075121,157263470533, 1341634934313,11445660526685,97644405002913, 833017002919477,7106575406263641, 60627110644694861,517217694177199185, 4412450805016013221] |