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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 20 |
| 5 | 71 |
| 6 | 262 |
| 7 | 994 |
| 8 | 3852 |
| 9 | 15183 |
| 10 | 60686 |
| 11 | 245412 |
| 12 | 1002344 |
| 13 | 4129012 |
| 14 | 17135432 |
| 15 | 71575350 |
| 16 | 300690836 |
| 17 | 1269662127 |
| 18 | 5385593406 |
| 19 | 22938095326 |
| 20 | 98059308676 |
| 21 | 420610907183 |
| 22 | 1809690341366 |
| 23 | 7808145901068 |
| 24 | 33776362530776 |
[1,1,2,6,20,71,262,994,3852,15183,60686,245412, 1002344,4129012,17135432,71575350,300690836, 1269662127,5385593406,22938095326,98059308676, 420610907183,1809690341366,7808145901068, 33776362530776] |