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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 6 |
| 2 | 168 |
| 3 | 1404 |
| 4 | 6720 |
| 5 | 23250 |
| 6 | 65016 |
| 7 | 156408 |
| 8 | 336384 |
| 9 | 663390 |
| 10 | 1221000 |
| 11 | 2124276 |
| 12 | 3526848 |
| 13 | 5628714 |
| 14 | 8684760 |
| 15 | 13014000 |
| 16 | 19009536 |
| 17 | 27149238 |
| 18 | 38007144 |
| 19 | 52265580 |
| 20 | 70728000 |
| 21 | 94332546 |
| 22 | 124166328 |
| 23 | 161480424 |
| 24 | 207705600 |
| 25 | 264468750 |
| 26 | 333610056 |
| 27 | 417200868 |
| 28 | 517562304 |
[0,6,168,1404,6720,23250,65016,156408,336384, 663390,1221000,2124276,3526848,5628714,8684760, 13014000,19009536,27149238,38007144,52265580, 70728000,94332546,124166328,161480424,207705600, 264468750,333610056,417200868,517562304] |