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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 4 |
| 2 | 48 |
| 3 | 480 |
| 4 | 4560 |
| 5 | 42504 |
| 6 | 393120 |
| 7 | 3624768 |
| 8 | 33390720 |
| 9 | 307618740 |
| 10 | 2835722032 |
| 11 | 26162863584 |
| 12 | 241614915360 |
| 13 | 2233533229200 |
| 14 | 20667453710400 |
| 15 | 191422799835264 |
| 16 | 1774573628661504 |
| 17 | 16465220088660432 |
| 18 | 152894968403313600 |
| 19 | 1420856831349155200 |
| 20 | 13213537097286612240 |
[0,4,48,480,4560,42504,393120,3624768,33390720, 307618740,2835722032,26162863584,241614915360, 2233533229200,20667453710400,191422799835264, 1774573628661504,16465220088660432, 152894968403313600,1420856831349155200, 13213537097286612240] |