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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 14 |
| 4 | 88 |
| 5 | 670 |
| 6 | 6170 |
| 7 | 66360 |
| 8 | 815640 |
| 9 | 11272800 |
| 10 | 173132400 |
| 11 | 2925014400 |
| 12 | 53909394000 |
| 13 | 1076365290000 |
| 14 | 23144112591600 |
| 15 | 533193460800000 |
| 16 | 13102608591072000 |
| 17 | 342105146182800000 |
| 18 | 9457689380931792000 |
| 19 | 275988880808825184000 |
| 20 | 8477631163592791200000 |
| 21 | 273430368958004818560000 |
| 22 | 9238944655686318693120000 |
[1,1,3,14,88,670,6170,66360,815640,11272800, 173132400,2925014400,53909394000,1076365290000, 23144112591600,533193460800000,13102608591072000, 342105146182800000,9457689380931792000, 275988880808825184000,8477631163592791200000, 273430368958004818560000, 9238944655686318693120000] |