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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 33 |
| 5 | 170 |
| 6 | 1170 |
| 7 | 10962 |
| 8 | 172844 |
| 9 | 4944024 |
| 10 | 270116280 |
| 11 | 28022441260 |
| 12 | 5448008695536 |
| 13 | 1969579223350128 |
| 14 | 1321964082404214704 |
| 15 | 1649890513414726210320 |
| 16 | 3840060942271653473695680 |
| 17 | 16723638762440239422492944768 |
| 18 | 136749695973639295091912681599872 |
[0,1,6,33,170,1170,10962,172844,4944024,270116280, 28022441260,5448008695536,1969579223350128, 1321964082404214704,1649890513414726210320, 3840060942271653473695680, 16723638762440239422492944768, 136749695973639295091912681599872] |