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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 72 |
| 6 | 230 |
| 7 | 692 |
| 8 | 2004 |
| 9 | 5683 |
| 10 | 15948 |
| 11 | 44523 |
| 12 | 123924 |
| 13 | 344113 |
| 14 | 953353 |
| 15 | 2635064 |
| 16 | 7266192 |
| 17 | 19990484 |
| 18 | 54876361 |
| 19 | 150331490 |
| 20 | 411034895 |
| 21 | 1121843295 |
| 22 | 3056805471 |
| 23 | 8316456845 |
| 24 | 22593934835 |
| 25 | 61301610481 |
| 26 | 166118362404 |
| 27 | 449639670226 |
[1,2,6,21,72,230,692,2004,5683,15948,44523,123924, 344113,953353,2635064,7266192,19990484,54876361, 150331490,411034895,1121843295,3056805471, 8316456845,22593934835,61301610481,166118362404, 449639670226] |