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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 240 |
| 5 | 80400 |
| 6 | 4012560 |
| 7 | 76848240 |
| 8 | 825447840 |
| 9 | 6005512800 |
| 10 | 33014872800 |
| 11 | 146953113120 |
| 12 | 554770648080 |
| 13 | 1835249610480 |
| 14 | 5448481998960 |
| 15 | 14778817981200 |
| 16 | 37135461679680 |
| 17 | 87386816771520 |
| 18 | 194264943433920 |
| 19 | 410876964198720 |
| 20 | 831638579799600 |
| 21 | 1618744884780240 |
[0,0,0,0,240,80400,4012560,76848240,825447840, 6005512800,33014872800,146953113120,554770648080, 1835249610480,5448481998960,14778817981200, 37135461679680,87386816771520,194264943433920, 410876964198720,831638579799600,1618744884780240] |