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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 8 |
| 5 | 24 |
| 6 | 168 |
| 7 | 876 |
| 8 | 1056 |
| 9 | 11232 |
| 10 | 92760 |
| 11 | 180944 |
| 12 | 4010832 |
| 13 | 27644436 |
| 14 | 93648672 |
| 15 | 1101958000 |
| 16 | 10436655840 |
| 17 | 27621623160 |
| 18 | 584607107256 |
| 19 | 5792507548200 |
| 20 | 21804094801440 |
| 21 | 316556065451520 |
| 22 | 2811301938708480 |
| 23 | 21826781430144768 |
| 24 | 297303503947693536 |
| 25 | 4153310734233341952 |
[1,1,1,4,8,24,168,876,1056,11232,92760,180944, 4010832,27644436,93648672,1101958000,10436655840, 27621623160,584607107256,5792507548200, 21804094801440,316556065451520,2811301938708480, 21826781430144768,297303503947693536, 4153310734233341952] |