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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 7 |
| 3 | 53 |
| 4 | 434 |
| 5 | 3886 |
| 6 | 38052 |
| 7 | 406260 |
| 8 | 4708368 |
| 9 | 58959216 |
| 10 | 794092320 |
| 11 | 11454567840 |
| 12 | 176267145600 |
| 13 | 2883327788160 |
| 14 | 49972442123520 |
| 15 | 914939341344000 |
| 16 | 17648374867200000 |
| 17 | 357763095454464000 |
| 18 | 7604722004802048000 |
| 19 | 169148296960860672000 |
| 20 | 3929342722459564032000 |
| 21 | 95164717841561217024000 |
[1,7,53,434,3886,38052,406260,4708368,58959216, 794092320,11454567840,176267145600,2883327788160, 49972442123520,914939341344000,17648374867200000, 357763095454464000,7604722004802048000, 169148296960860672000,3929342722459564032000, 95164717841561217024000] |