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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 24 |
| 5 | 60 |
| 6 | 480 |
| 7 | 5250 |
| 8 | 40656 |
| 9 | 302904 |
| 10 | 3024720 |
| 11 | 35260830 |
| 12 | 400499880 |
| 13 | 4619610996 |
| 14 | 58758862344 |
| 15 | 813678468330 |
| 16 | 11686918766880 |
| 17 | 173172973038960 |
| 18 | 2695921067029536 |
| 19 | 44219170187746614 |
| 20 | 755363769931590840 |
| 21 | 13351503268881437100 |
| 22 | 244634794020399856920 |
[1,0,0,6,24,60,480,5250,40656,302904,3024720, 35260830,400499880,4619610996,58758862344, 813678468330,11686918766880,173172973038960, 2695921067029536,44219170187746614, 755363769931590840,13351503268881437100, 244634794020399856920] |