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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 14 |
| 4 | 104 |
| 5 | 976 |
| 6 | 11616 |
| 7 | 161472 |
| 8 | 2582016 |
| 9 | 46451712 |
| 10 | 929003520 |
| 11 | 20437463040 |
| 12 | 490498375680 |
| 13 | 12752940072960 |
| 14 | 357082301399040 |
| 15 | 10712468463943680 |
| 16 | 342798990185594880 |
| 17 | 11655165645170933760 |
| 18 | 419585963202371911680 |
| 19 | 15944266600833991311360 |
| 20 | 637770664032408384307200 |
[1,1,3,14,104,976,11616,161472,2582016,46451712, 929003520,20437463040,490498375680,12752940072960, 357082301399040,10712468463943680, 342798990185594880,11655165645170933760, 419585963202371911680,15944266600833991311360, 637770664032408384307200] |