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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 72 |
| 6 | 230 |
| 7 | 689 |
| 8 | 1970 |
| 9 | 5460 |
| 10 | 14833 |
| 11 | 39790 |
| 12 | 105890 |
| 13 | 280367 |
| 14 | 739878 |
| 15 | 1948186 |
| 16 | 5121973 |
| 17 | 13451620 |
| 18 | 35299782 |
| 19 | 92580429 |
| 20 | 242705586 |
| 21 | 636062896 |
| 22 | 1666534337 |
| 23 | 4365640346 |
| 24 | 11434584546 |
| 25 | 29946505947 |
| 26 | 78421715110 |
| 27 | 205352199014 |
[1,2,6,21,72,230,689,1970,5460,14833,39790,105890, 280367,739878,1948186,5121973,13451620,35299782, 92580429,242705586,636062896,1666534337, 4365640346,11434584546,29946505947,78421715110, 205352199014] |