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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 14 |
| 5 | 30 |
| 6 | 540 |
| 7 | 1806 |
| 8 | 40824 |
| 9 | 186480 |
| 10 | 5103000 |
| 11 | 29607600 |
| 12 | 953029440 |
| 13 | 6711344640 |
| 14 | 248619571200 |
| 15 | 2060056318320 |
| 16 | 86355926616960 |
| 17 | 823172919528960 |
| 18 | 38528927611574400 |
| 19 | 415357755774998400 |
| 20 | 21473732319740064000 |
| 21 | 258323865658578720000 |
| 22 | 14620825330739032204800 |
[1,0,1,1,14,30,540,1806,40824,186480,5103000, 29607600,953029440,6711344640,248619571200, 2060056318320,86355926616960,823172919528960, 38528927611574400,415357755774998400, 21473732319740064000,258323865658578720000, 14620825330739032204800] |