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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 720 |
| 3 | 13440 |
| 4 | 97200 |
| 5 | 455040 |
| 6 | 1714320 |
| 7 | 4821120 |
| 8 | 12380400 |
| 9 | 29043840 |
| 10 | 58980960 |
| 11 | 114076800 |
| 12 | 219310320 |
| 13 | 367338240 |
| 14 | 621878400 |
| 15 | 1037727360 |
| 16 | 1583679600 |
| 17 | 2401816320 |
| 18 | 3747180240 |
| 19 | 5232470400 |
| 20 | 7551983520 |
| 21 | 10938261120 |
| 22 | 14715224640 |
| 23 | 19930775040 |
| 24 | 28073386800 |
| 25 | 35727920640 |
[1,0,720,13440,97200,455040,1714320,4821120, 12380400,29043840,58980960,114076800,219310320, 367338240,621878400,1037727360,1583679600, 2401816320,3747180240,5232470400,7551983520, 10938261120,14715224640,19930775040,28073386800, 35727920640] |