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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 16 |
| 5 | 44 |
| 6 | 122 |
| 7 | 342 |
| 8 | 966 |
| 9 | 2746 |
| 10 | 7846 |
| 11 | 22514 |
| 12 | 64836 |
| 13 | 187288 |
| 14 | 542438 |
| 15 | 1574666 |
| 16 | 4580400 |
| 17 | 13347324 |
| 18 | 38956182 |
| 19 | 113861922 |
| 20 | 333226560 |
| 21 | 976353876 |
| 22 | 2863756158 |
| 23 | 8407877394 |
| 24 | 24707200854 |
| 25 | 72663608178 |
| 26 | 213864889770 |
| 27 | 629893319902 |
[1,1,2,6,16,44,122,342,966,2746,7846,22514,64836, 187288,542438,1574666,4580400,13347324,38956182, 113861922,333226560,976353876,2863756158, 8407877394,24707200854,72663608178,213864889770, 629893319902] |