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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 6 |
| 5 | 40 |
| 6 | 120 |
| 7 | 5040 |
| 8 | 1008 |
| 9 | 362880 |
| 10 | 362880 |
| 11 | 13305600 |
| 12 | 39916800 |
| 13 | 6227020800 |
| 14 | 6227020800 |
| 15 | 1307674368000 |
| 16 | 1307674368000 |
| 17 | 39520825344000 |
| 18 | 14227497123840 |
| 19 | 121645100408832000 |
| 20 | 121645100408832000 |
| 21 | 51090942171709440000 |
| 22 | 51090942171709440000 |
[1,1,1,6,6,40,120,5040,1008,362880,362880, 13305600,39916800,6227020800,6227020800, 1307674368000,1307674368000,39520825344000, 14227497123840,121645100408832000, 121645100408832000,51090942171709440000, 51090942171709440000] |