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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | -1 |
| 3 | -5 |
| 4 | -26 |
| 5 | -154 |
| 6 | -1044 |
| 7 | -8028 |
| 8 | -69264 |
| 9 | -663696 |
| 10 | -6999840 |
| 11 | -80627040 |
| 12 | -1007441280 |
| 13 | -13575738240 |
| 14 | -196287356160 |
| 15 | -3031488633600 |
| 16 | -49811492505600 |
| 17 | -867718162483200 |
| 18 | -15974614352793600 |
| 19 | -309920046408806400 |
| 20 | -6320046028584960000 |
[1,0,-1,-5,-26,-154,-1044,-8028,-69264,-663696, -6999840,-80627040,-1007441280,-13575738240, -196287356160,-3031488633600,-49811492505600, -867718162483200,-15974614352793600, -309920046408806400,-6320046028584960000] |