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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 0 |
| 4 | 16 |
| 5 | 40 |
| 6 | 192 |
| 7 | 560 |
| 8 | 3328 |
| 9 | 11772 |
| 10 | 63840 |
| 11 | 259336 |
| 12 | 1550976 |
| 13 | 7169656 |
| 14 | 42410256 |
| 15 | 234044160 |
| 16 | 1366190592 |
[1,4,0,16,40,192,560,3328,11772,63840,259336, 1550976,7169656,42410256,234044160,1366190592] |