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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 8 |
| 3 | 88 |
| 4 | 720 |
| 5 | 5360 |
| 6 | 38488 |
| 7 | 272328 |
| 8 | 1915040 |
| 9 | 13431520 |
| 10 | 94099368 |
| 11 | 658931768 |
| 12 | 4613230960 |
| 13 | 32294742480 |
| 14 | 226069574648 |
| 15 | 1582506154408 |
| 16 | 11077600476480 |
| 17 | 77543375522240 |
| 18 | 542804145216328 |
| 19 | 3799630566196248 |
| 20 | 26597418612419600 |
| 21 | 186181944234074800 |
| 22 | 1303273651479936408 |
[0,0,8,88,720,5360,38488,272328,1915040,13431520, 94099368,658931768,4613230960,32294742480, 226069574648,1582506154408,11077600476480, 77543375522240,542804145216328,3799630566196248, 26597418612419600,186181944234074800, 1303273651479936408] |