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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 20 |
| 2 | 252 |
| 3 | 2860 |
| 4 | 30940 |
| 5 | 325584 |
| 6 | 3364900 |
| 7 | 34337160 |
| 8 | 347103900 |
| 9 | 3483301360 |
| 10 | 34754081648 |
| 11 | 345120260940 |
| 12 | 3413758188932 |
| 13 | 33655718658800 |
| 14 | 330869721936600 |
| 15 | 3244839440755920 |
| 16 | 31754250910172700 |
| 17 | 310165459118369712 |
| 18 | 3024542552887591120 |
| 19 | 29449493278116018800 |
| 20 | 286360607519186119920 |
[1,20,252,2860,30940,325584,3364900,34337160, 347103900,3483301360,34754081648,345120260940, 3413758188932,33655718658800,330869721936600, 3244839440755920,31754250910172700, 310165459118369712,3024542552887591120, 29449493278116018800,286360607519186119920] |