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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 9 |
| 5 | 54 |
| 6 | 0 |
| 7 | 0 |
| 8 | 52650 |
| 9 | 1890540 |
| 10 | 0 |
| 11 | 0 |
| 12 | 264480947280 |
| 13 | 57127543673760 |
| 14 | 0 |
| 15 | 0 |
| 16 | 1295355012667626301200 |
| 17 | 1678780080964997690732640 |
| 18 | 0 |
| 19 | 0 |
| 20 | 6577809875294796334824189267538944 |
[1,0,0,9,54,0,0,52650,1890540,0,0,264480947280, 57127543673760,0,0,1295355012667626301200, 1678780080964997690732640,0,0, 6577809875294796334824189267538944] |