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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 90 |
| 4 | 1879 |
| 5 | 47024 |
| 6 | 1331664 |
| 7 | 41250519 |
| 8 | 1367533365 |
| 9 | 47808569835 |
| 10 | 1744233181074 |
| 11 | 65905305836049 |
| 12 | 2564220925607625 |
| 13 | 102277575120518170 |
| 14 | 4167486279986250932 |
| 15 | 172988069360147449566 |
| 16 | 7298137818882637998561 |
| 17 | 312349784398279829229533 |
| 18 | 13539988681466075755541070 |
[1,1,6,90,1879,47024,1331664,41250519,1367533365, 47808569835,1744233181074,65905305836049, 2564220925607625,102277575120518170, 4167486279986250932,172988069360147449566, 7298137818882637998561,312349784398279829229533, 13539988681466075755541070] |