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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 20 |
| 3 | 1680 |
| 4 | 369600 |
| 5 | 168168000 |
| 6 | 137127810959 |
| 7 | 182138398520387 |
| 8 | 367988956112888200 |
| 9 | 1074073326771101149080 |
| 10 | 4350318942513425384777400 |
| 11 | 23673963203663687592089088600 |
| 12 | 168569155472096397352266896207243 |
| 13 | 1536148007688582239667327040442799059 |
[1,1,20,1680,369600,168168000,137127810959, 182138398520387,367988956112888200, 1074073326771101149080,4350318942513425384777400, 23673963203663687592089088600, 168569155472096397352266896207243, 1536148007688582239667327040442799059] |