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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 23 |
| 5 | 104 |
| 6 | 532 |
| 7 | 3004 |
| 8 | 18426 |
| 9 | 121393 |
| 10 | 851810 |
| 11 | 6325151 |
| 12 | 49448313 |
| 13 | 405298482 |
| 14 | 3470885747 |
| 15 | 30965656442 |
| 16 | 287083987270 |
| 17 | 2759838731485 |
| 18 | 27458514900626 |
| 19 | 282264050120512 |
| 20 | 2993392570828096 |
| 21 | 32704759586810036 |
| 22 | 367673428857985261 |
[1,1,2,6,23,104,532,3004,18426,121393,851810, 6325151,49448313,405298482,3470885747,30965656442, 287083987270,2759838731485,27458514900626, 282264050120512,2993392570828096, 32704759586810036,367673428857985261] |