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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 5 |
| 3 | 23 |
| 4 | 146 |
| 5 | 874 |
| 6 | 8124 |
| 7 | 62628 |
| 8 | 707664 |
| 9 | 7860816 |
| 10 | 103284000 |
| 11 | 1179669600 |
| 12 | 24454569600 |
| 13 | 324615427200 |
| 14 | 5740203974400 |
| 15 | 119579523436800 |
| 16 | 2688723275212800 |
| 17 | 46084905896601600 |
| 18 | 1383333631684300800 |
| 19 | 26411386476116275200 |
| 20 | 868104140064602112000 |
[1,5,23,146,874,8124,62628,707664,7860816, 103284000,1179669600,24454569600,324615427200, 5740203974400,119579523436800,2688723275212800, 46084905896601600,1383333631684300800, 26411386476116275200,868104140064602112000] |