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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 20 |
| 2 | 1456 |
| 3 | 223040 |
| 4 | 58575616 |
| 5 | 23502402560 |
| 6 | 13373331582976 |
| 7 | 10243813494702080 |
| 8 | 10163266698756161536 |
| 9 | 12678333853101857177600 |
| 10 | 19422906944247900899639296 |
| 11 | 35848212199606304514894725120 |
| 12 | 78455159096957357408585311584256 |
| 13 | 200891413690245126967691882151280640 |
[1,20,1456,223040,58575616,23502402560, 13373331582976,10243813494702080, 10163266698756161536,12678333853101857177600, 19422906944247900899639296, 35848212199606304514894725120, 78455159096957357408585311584256, 200891413690245126967691882151280640] |