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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 41 |
| 3 | 281 |
| 4 | 1926 |
| 5 | 13201 |
| 6 | 90481 |
| 7 | 620166 |
| 8 | 4250681 |
| 9 | 29134601 |
| 10 | 199691526 |
| 11 | 1368706081 |
| 12 | 9381251041 |
| 13 | 64300051206 |
| 14 | 440719107401 |
| 15 | 3020733700601 |
| 16 | 20704416796806 |
| 17 | 141910183877041 |
| 18 | 972666870342481 |
[1,6,41,281,1926,13201,90481,620166,4250681, 29134601,199691526,1368706081,9381251041, 64300051206,440719107401,3020733700601, 20704416796806,141910183877041,972666870342481] |