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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 33 |
| 4 | 472 |
| 5 | 4745 |
| 6 | 99216 |
| 7 | 1456273 |
| 8 | 39669120 |
| 9 | 769528593 |
| 10 | 25737068800 |
| 11 | 622548099041 |
| 12 | 24632715009024 |
| 13 | 715109889035737 |
| 14 | 32630102257170432 |
| 15 | 1106618435304908625 |
| 16 | 57151019891266256896 |
| 17 | 2219208490411286184737 |
| 18 | 127876294410780326952960 |
[1,1,6,33,472,4745,99216,1456273,39669120, 769528593,25737068800,622548099041,24632715009024, 715109889035737,32630102257170432, 1106618435304908625,57151019891266256896, 2219208490411286184737,127876294410780326952960] |