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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 9 |
| 3 | 307 |
| 4 | 2610 |
| 5 | 88741 |
| 6 | 754299 |
| 7 | 25646167 |
| 8 | 217992420 |
| 9 | 7411742281 |
| 10 | 62999809389 |
| 11 | 2141993519227 |
| 12 | 18206944913430 |
| 13 | 619036127056621 |
| 14 | 5261807079981279 |
| 15 | 178901440719363487 |
| 16 | 1520662246114589640 |
| 17 | 51702516367896047761 |
[0,1,9,307,2610,88741,754299,25646167,217992420, 7411742281,62999809389,2141993519227, 18206944913430,619036127056621,5261807079981279, 178901440719363487,1520662246114589640, 51702516367896047761] |