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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 11 |
| 3 | 68 |
| 4 | 467 |
| 5 | 3418 |
| 6 | 26133 |
| 7 | 206264 |
| 8 | 1667908 |
| 9 | 13746476 |
| 10 | 115050074 |
| 11 | 975180582 |
| 12 | 8354044986 |
| 13 | 72215867960 |
| 14 | 629139381448 |
| 15 | 5518236646614 |
| 16 | 48689379017014 |
| 17 | 431868759238498 |
| 18 | 3848616161600778 |
| 19 | 34441553184113542 |
| 20 | 309390614528633311 |
| 21 | 2788841905397090626 |
[1,2,11,68,467,3418,26133,206264,1667908,13746476, 115050074,975180582,8354044986,72215867960, 629139381448,5518236646614,48689379017014, 431868759238498,3848616161600778, 34441553184113542,309390614528633311, 2788841905397090626] |