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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 17 |
| 4 | 74 |
| 5 | 514 |
| 6 | 3564 |
| 7 | 30708 |
| 8 | 250704 |
| 9 | 2780496 |
| 10 | 29982240 |
| 11 | 373350240 |
| 12 | 4639870080 |
| 13 | 67024333440 |
| 14 | 988156834560 |
| 15 | 16914631507200 |
| 16 | 271941778483200 |
| 17 | 4999620452198400 |
| 18 | 94617104704819200 |
| 19 | 1925772463506124800 |
| 20 | 39245319872575488000 |
| 21 | 902004581585737728000 |
[1,3,17,74,514,3564,30708,250704,2780496,29982240, 373350240,4639870080,67024333440,988156834560, 16914631507200,271941778483200,4999620452198400, 94617104704819200,1925772463506124800, 39245319872575488000,902004581585737728000] |