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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 21 |
| 4 | 183 |
| 5 | 2362 |
| 6 | 42449 |
| 7 | 1012897 |
| 8 | 30961412 |
| 9 | 1179154241 |
| 10 | 54727128731 |
| 11 | 3040047461530 |
| 12 | 199109235070645 |
| 13 | 15182265283487213 |
| 14 | 1333242114217704924 |
| 15 | 133577535961042535669 |
| 16 | 15144191953510005439455 |
| 17 | 1928873660857769308675146 |
| 18 | 274228718414760130917382185 |
[1,1,4,21,183,2362,42449,1012897,30961412, 1179154241,54727128731,3040047461530, 199109235070645,15182265283487213, 1333242114217704924,133577535961042535669, 15144191953510005439455,1928873660857769308675146, 274228718414760130917382185] |