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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 12 |
| 3 | 84 |
| 4 | 3960 |
| 5 | 27144 |
| 6 | 1275204 |
| 7 | 8740380 |
| 8 | 410611824 |
| 9 | 2814375312 |
| 10 | 132215732220 |
| 11 | 906220110180 |
| 12 | 42573055163112 |
| 13 | 291800061102744 |
| 14 | 13708391546789940 |
| 15 | 93958713454973484 |
| 16 | 4414059505011197664 |
| 17 | 30254413932440359200 |
| 18 | 1421313452222058857964 |
[0,12,84,3960,27144,1275204,8740380,410611824, 2814375312,132215732220,906220110180, 42573055163112,291800061102744,13708391546789940, 93958713454973484,4414059505011197664, 30254413932440359200,1421313452222058857964] |