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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 14 |
| 5 | 39 |
| 6 | 109 |
| 7 | 308 |
| 8 | 876 |
| 9 | 2502 |
| 10 | 7174 |
| 11 | 20642 |
| 12 | 59572 |
| 13 | 172375 |
| 14 | 499936 |
| 15 | 1452939 |
| 16 | 4230353 |
| 17 | 12337274 |
| 18 | 36033281 |
| 19 | 105382550 |
| 20 | 308574692 |
| 21 | 904548474 |
| 22 | 2654253082 |
| 23 | 7795709736 |
| 24 | 22916057914 |
| 25 | 67416582519 |
| 26 | 198477304237 |
| 27 | 584722289762 |
[1,1,2,5,14,39,109,308,876,2502,7174,20642,59572, 172375,499936,1452939,4230353,12337274,36033281, 105382550,308574692,904548474,2654253082, 7795709736,22916057914,67416582519,198477304237, 584722289762] |