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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 2 |
| 4 | 8 |
| 5 | 72 |
| 6 | 272 |
| 7 | 128 |
| 8 | 1024 |
| 9 | 51264 |
| 10 | 275072 |
| 11 | -1287680 |
| 12 | -7871488 |
| 13 | 206883328 |
| 14 | 1471104000 |
| 15 | -19670491136 |
| 16 | -159374082048 |
| 17 | 3293417492480 |
| 18 | 29559475576832 |
| 19 | -595302140223488 |
| 20 | -5903345189421056 |
| 21 | 137666774002696192 |
[0,1,2,2,8,72,272,128,1024,51264,275072,-1287680, -7871488,206883328,1471104000,-19670491136, -159374082048,3293417492480,29559475576832, -595302140223488,-5903345189421056, 137666774002696192] |