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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 5 |
| 3 | 53 |
| 4 | 884 |
| 5 | 20234 |
| 6 | 589834 |
| 7 | 20903700 |
| 8 | 872660256 |
| 9 | 41944510752 |
| 10 | 2281437791448 |
| 11 | 138539360885760 |
| 12 | 9290720296262976 |
| 13 | 681965664411820944 |
| 14 | 54384461861952738528 |
| 15 | 4682101594725064872768 |
| 16 | 432815761314471190599936 |
| 17 | 42757813607285233998385920 |
| 18 | 4495579313771176952867958528 |
[1,1,5,53,884,20234,589834,20903700,872660256, 41944510752,2281437791448,138539360885760, 9290720296262976,681965664411820944, 54384461861952738528,4682101594725064872768, 432815761314471190599936, 42757813607285233998385920, 4495579313771176952867958528] |