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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 9 |
| 3 | 54 |
| 4 | 404 |
| 5 | 3598 |
| 6 | 37003 |
| 7 | 430300 |
| 8 | 5571147 |
| 9 | 79358032 |
| 10 | 1231990840 |
| 11 | 20684884234 |
| 12 | 373208232229 |
| 13 | 7197079035318 |
| 14 | 147658793214733 |
| 15 | 3210107125516682 |
| 16 | 73690798853163884 |
| 17 | 1780718798351625094 |
| 18 | 45171972342078432287 |
| 19 | 1199948465249850848608 |
| 20 | 33305064129201851432591 |
| 21 | 963911863209583899492324 |
[1,2,9,54,404,3598,37003,430300,5571147,79358032, 1231990840,20684884234,373208232229,7197079035318, 147658793214733,3210107125516682, 73690798853163884,1780718798351625094, 45171972342078432287,1199948465249850848608, 33305064129201851432591,963911863209583899492324] |