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A144085 as a simple table
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 18 |
| 4 | 108 |
| 5 | 780 |
| 6 | 6600 |
| 7 | 63840 |
| 8 | 693840 |
| 9 | 8361360 |
| 10 | 110557440 |
| 11 | 1590351840 |
| 12 | 24713156160 |
| 13 | 412393101120 |
| 14 | 7352537512320 |
| 15 | 139443752448000 |
| 16 | 2802408959750400 |
| 17 | 59479486120454400 |
| 18 | 1329239028813696000 |
| 19 | 31194214921732262400 |
| 20 | 766888191387539020800 |
| 21 | 19707387644116280908800 |
| 22 | 528327710066244459571200 |
[1,1,4,18,108,780,6600,63840,693840,8361360, 110557440,1590351840,24713156160,412393101120, 7352537512320,139443752448000,2802408959750400, 59479486120454400,1329239028813696000, 31194214921732262400,766888191387539020800, 19707387644116280908800,528327710066244459571200] |