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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 9 |
| 3 | 76 |
| 4 | 639 |
| 5 | 5371 |
| 6 | 45144 |
| 7 | 379441 |
| 8 | 3189249 |
| 9 | 26806036 |
| 10 | 225308079 |
| 11 | 1893742531 |
| 12 | 15917142384 |
| 13 | 133785568801 |
| 14 | 1124484407289 |
| 15 | 9451431821596 |
| 16 | 79440464357919 |
| 17 | 667707020113291 |
| 18 | 5612160859230024 |
| 19 | 47170912632503761 |
| 20 | 396477409396383729 |
| 21 | 3332442121404934756 |
[0,1,9,76,639,5371,45144,379441,3189249,26806036, 225308079,1893742531,15917142384,133785568801, 1124484407289,9451431821596,79440464357919, 667707020113291,5612160859230024, 47170912632503761,396477409396383729, 3332442121404934756] |