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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 12 |
| 3 | 108 |
| 4 | 800 |
| 5 | 5250 |
| 6 | 31752 |
| 7 | 181104 |
| 8 | 988416 |
| 9 | 5212350 |
| 10 | 26741000 |
| 11 | 134132856 |
| 12 | 660284352 |
| 13 | 3199016548 |
| 14 | 15288882000 |
| 15 | 72209880000 |
| 16 | 337535723520 |
| 17 | 1563410094390 |
| 18 | 7182839945160 |
| 19 | 32761238433000 |
| 20 | 148450107960000 |
| 21 | 668693511305820 |
| 22 | 2995943329133040 |
| 23 | 13356820221694560 |
[0,1,12,108,800,5250,31752,181104,988416,5212350, 26741000,134132856,660284352,3199016548, 15288882000,72209880000,337535723520, 1563410094390,7182839945160,32761238433000, 148450107960000,668693511305820,2995943329133040, 13356820221694560] |