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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 16 |
| 6 | 126 |
| 7 | 672 |
| 8 | 2772 |
| 9 | 9504 |
| 10 | 28314 |
| 11 | 75504 |
| 12 | 184041 |
| 13 | 416416 |
| 14 | 884884 |
| 15 | 1782144 |
| 16 | 3426384 |
| 17 | 6325632 |
| 18 | 11267532 |
| 19 | 19442016 |
| 20 | 32605881 |
| 21 | 53300016 |
| 22 | 85131970 |
| 23 | 133138720 |
| 24 | 204246900 |
| 25 | 307850400 |
| 26 | 456528150 |
| 27 | 666928080 |
| 28 | 960846705 |
| 29 | 1366537536 |
| 30 | 1920285576 |
| 31 | 2668289536 |
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