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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 21 |
| 5 | 86 |
| 6 | 396 |
| 7 | 1812 |
| 8 | 8607 |
| 9 | 41958 |
| 10 | 207333 |
| 11 | 1040234 |
| 12 | 5281965 |
| 13 | 27078756 |
| 14 | 140021248 |
| 15 | 729369474 |
| 16 | 3823598232 |
| 17 | 20158251814 |
| 18 | 106809280563 |
| 19 | 568471343322 |
| 20 | 3037782047947 |
| 21 | 16292380484454 |
| 22 | 87669285293451 |
| 23 | 473172657154822 |
[1,1,1,6,21,86,396,1812,8607,41958,207333,1040234, 5281965,27078756,140021248,729369474,3823598232, 20158251814,106809280563,568471343322, 3037782047947,16292380484454,87669285293451, 473172657154822] |