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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 0 |
| 5 | 120 |
| 6 | 2880 |
| 7 | 2940 |
| 8 | 403200 |
| 9 | 8074080 |
| 10 | 47174400 |
| 11 | 3635866080 |
| 12 | 72648576000 |
| 13 | 1183289627520 |
| 14 | 71843629777920 |
| 15 | 1617274512453600 |
| 16 | 49788393887232000 |
| 17 | 2703881987142336000 |
| 18 | 74947823184858624000 |
| 19 | 3369543466000424993280 |
| 20 | 176517590187551348736000 |
[1,0,0,6,0,120,2880,2940,403200,8074080,47174400, 3635866080,72648576000,1183289627520, 71843629777920,1617274512453600,49788393887232000, 2703881987142336000,74947823184858624000, 3369543466000424993280,176517590187551348736000] |