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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 20 |
| 4 | 282 |
| 5 | 5134 |
| 6 | 112053 |
| 7 | 2823119 |
| 8 | 80202565 |
| 9 | 2529045393 |
| 10 | 87523776013 |
| 11 | 3295995672161 |
| 12 | 134155142687732 |
| 13 | 5869278171065418 |
| 14 | 274718037952537674 |
| 15 | 13701118397652347442 |
| 16 | 725505704889894172448 |
| 17 | 40658992718689480518864 |
| 18 | 2404662897766073643050293 |
| 19 | 149692182669205551972626617 |
| 20 | 9784886698908632846522031701 |
[1,1,2,20,282,5134,112053,2823119,80202565, 2529045393,87523776013,3295995672161, 134155142687732,5869278171065418, 274718037952537674,13701118397652347442, 725505704889894172448,40658992718689480518864, 2404662897766073643050293, 149692182669205551972626617, 9784886698908632846522031701] |