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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 13 |
| 3 | 96 |
| 4 | 753 |
| 5 | 6120 |
| 6 | 50927 |
| 7 | 430992 |
| 8 | 3694093 |
| 9 | 31978904 |
| 10 | 279059428 |
| 11 | 2451295616 |
| 12 | 21652137343 |
| 13 | 192157404920 |
| 14 | 1712319819482 |
| 15 | 15312962637856 |
| 16 | 137371506939205 |
| 17 | 1235792077831416 |
| 18 | 11144956230810508 |
| 19 | 100736768308585216 |
| 20 | 912394194390216484 |
| 21 | 8279093240641977248 |
[1,2,13,96,753,6120,50927,430992,3694093,31978904, 279059428,2451295616,21652137343,192157404920, 1712319819482,15312962637856,137371506939205, 1235792077831416,11144956230810508, 100736768308585216,912394194390216484, 8279093240641977248] |