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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 16 |
| 5 | 45 |
| 6 | 126 |
| 7 | 356 |
| 8 | 1008 |
| 9 | 2862 |
| 10 | 8140 |
| 11 | 23188 |
| 12 | 66144 |
| 13 | 188916 |
| 14 | 540216 |
| 15 | 1546560 |
| 16 | 4432512 |
| 17 | 12717513 |
| 18 | 36526626 |
| 19 | 105016686 |
| 20 | 302228080 |
| 21 | 870613689 |
| 22 | 2510249302 |
| 23 | 7244285436 |
| 24 | 20924179920 |
| 25 | 60487084775 |
| 26 | 174994990326 |
| 27 | 506669921982 |
[1,2,6,16,45,126,356,1008,2862,8140,23188,66144, 188916,540216,1546560,4432512,12717513,36526626, 105016686,302228080,870613689,2510249302, 7244285436,20924179920,60487084775,174994990326, 506669921982] |