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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 640 |
| 7 | 4164 |
| 8 | 28224 |
| 9 | 237168 |
| 10 | 2133992 |
| 11 | 21136148 |
| 12 | 226558932 |
| 13 | 2656690332 |
| 14 | 33144866692 |
| 15 | 444798029884 |
| 16 | 6309964631348 |
[1,2,6,24,120,640,4164,28224,237168,2133992, 21136148,226558932,2656690332,33144866692, 444798029884,6309964631348] |