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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | -3 |
| 5 | 0 |
| 6 | -18 |
| 7 | -12 |
| 8 | -87 |
| 9 | -120 |
| 10 | -432 |
| 11 | -840 |
| 12 | -2883 |
| 13 | -5208 |
| 14 | -21378 |
| 15 | -39876 |
| 16 | -144507 |
| 17 | -309456 |
| 18 | -978888 |
| 19 | -2349828 |
| 20 | -6995931 |
| 21 | -17727576 |
| 22 | -52099902 |
| 23 | -133195908 |
| 24 | -389599548 |
| 25 | -1010029956 |
| 26 | -2921670744 |
| 27 | -7740553548 |
[1,0,0,0,-3,0,-18,-12,-87,-120,-432,-840,-2883, -5208,-21378,-39876,-144507,-309456,-978888, -2349828,-6995931,-17727576,-52099902,-133195908, -389599548,-1010029956,-2921670744,-7740553548] |