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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 40 |
| 6 | 720 |
| 7 | 5040 |
| 8 | 13440 |
| 9 | 362880 |
| 10 | 3628800 |
| 11 | 13305600 |
| 12 | 479001600 |
| 13 | 889574400 |
| 14 | 29059430400 |
| 15 | 1307674368000 |
| 16 | 1609445376000 |
| 17 | 118562476032000 |
| 18 | 6402373705728000 |
| 19 | 121645100408832000 |
| 20 | 115852476579840000 |
[1,1,2,6,24,40,720,5040,13440,362880,3628800, 13305600,479001600,889574400,29059430400, 1307674368000,1609445376000,118562476032000, 6402373705728000,121645100408832000, 115852476579840000] |