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| n | a(n) |
|---|---|
| 2 | -1 |
| 3 | 0 |
| 4 | 28 |
| 5 | 192 |
| 6 | 880 |
| 7 | 3328 |
| 8 | 11200 |
| 9 | 34816 |
| 10 | 102144 |
| 11 | 286720 |
| 12 | 777216 |
| 13 | 2048000 |
| 14 | 5271552 |
| 15 | 13303808 |
| 16 | 33013760 |
| 17 | 80740352 |
| 18 | 194969600 |
| 19 | 465567744 |
| 20 | 1100742656 |
| 21 | 2579496960 |
| 22 | 5996806144 |
| 23 | 13841203200 |
| 24 | 31738298368 |
| 25 | 72343355392 |
| 26 | 163997286400 |
[-1,0,28,192,880,3328,11200,34816,102144,286720, 777216,2048000,5271552,13303808,33013760,80740352, 194969600,465567744,1100742656,2579496960, 5996806144,13841203200,31738298368,72343355392, 163997286400] |