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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 4 |
| 3 | 0 |
| 4 | 16 |
| 5 | 0 |
| 6 | 64 |
| 7 | 96 |
| 8 | 488 |
| 9 | 1392 |
| 10 | 5064 |
| 11 | 17856 |
| 12 | 65576 |
| 13 | 231728 |
| 14 | 863664 |
| 15 | 3313392 |
[0,4,0,16,0,64,96,488,1392,5064,17856,65576, 231728,863664,3313392] |