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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 23 |
| 4 | 143 |
| 5 | 1344 |
| 6 | 16476 |
| 7 | 248509 |
| 8 | 4519021 |
| 9 | 97094158 |
| 10 | 2419043330 |
| 11 | 68973522675 |
| 12 | 2228418011291 |
| 13 | 80844520830828 |
| 14 | 3266496719516152 |
| 15 | 145973848760893369 |
| 16 | 7172279845906943513 |
| 17 | 385419654638220638810 |
| 18 | 22543794177677289243966 |
| 19 | 1429137150185034529444879 |
| 20 | 97815341290407924477479399 |
[1,2,6,23,143,1344,16476,248509,4519021,97094158, 2419043330,68973522675,2228418011291, 80844520830828,3266496719516152, 145973848760893369,7172279845906943513, 385419654638220638810,22543794177677289243966, 1429137150185034529444879, 97815341290407924477479399] |