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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 44 |
| 4 | 320 |
| 5 | 2912 |
| 6 | 31808 |
| 7 | 405344 |
| 8 | 5903360 |
| 9 | 96722432 |
| 10 | 1760811008 |
| 11 | 35260703744 |
| 12 | 770296217600 |
| 13 | 18229999665152 |
| 14 | 464622502289408 |
| 15 | 12687528814751744 |
| 16 | 369557965317079040 |
| 17 | 11437129322496131072 |
| 18 | 374778854976227115008 |
| 19 | 12963259774166774841344 |
| 20 | 471986702056014668103680 |
[1,2,8,44,320,2912,31808,405344,5903360,96722432, 1760811008,35260703744,770296217600, 18229999665152,464622502289408,12687528814751744, 369557965317079040,11437129322496131072, 374778854976227115008,12963259774166774841344, 471986702056014668103680] |