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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 16 |
| 3 | 168 |
| 4 | 1986 |
| 5 | 25092 |
| 6 | 330816 |
| 7 | 4492560 |
| 8 | 62352720 |
| 9 | 879956000 |
| 10 | 12583279360 |
| 11 | 181872982400 |
| 12 | 2652039363240 |
| 13 | 38959845007440 |
| 14 | 575974743052800 |
| 15 | 8561706637619520 |
| 16 | 127874111328349890 |
| 17 | 1917875205285147780 |
[1,2,16,168,1986,25092,330816,4492560,62352720, 879956000,12583279360,181872982400,2652039363240, 38959845007440,575974743052800,8561706637619520, 127874111328349890,1917875205285147780] |