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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 76 |
| 6 | 270 |
| 7 | 930 |
| 8 | 3114 |
| 9 | 10196 |
| 10 | 32820 |
| 11 | 104283 |
| 12 | 328048 |
| 13 | 1023854 |
| 14 | 3175395 |
| 15 | 9797833 |
| 16 | 30104416 |
| 17 | 92174093 |
| 18 | 281393563 |
| 19 | 856933273 |
| 20 | 2604185761 |
| 21 | 7899961881 |
| 22 | 23928712717 |
| 23 | 72385213846 |
| 24 | 218724040451 |
| 25 | 660278241111 |
| 26 | 1991584682200 |
| 27 | 6002897801720 |
| 28 | 18082374709679 |
[1,1,2,6,21,76,270,930,3114,10196,32820,104283, 328048,1023854,3175395,9797833,30104416,92174093, 281393563,856933273,2604185761,7899961881, 23928712717,72385213846,218724040451,660278241111, 1991584682200,6002897801720,18082374709679] |