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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 44 |
| 5 | 160 |
| 6 | 630 |
| 7 | 2505 |
| 8 | 10274 |
| 9 | 42813 |
| 10 | 181411 |
| 11 | 778323 |
| 12 | 3376953 |
| 13 | 14792252 |
| 14 | 65335900 |
| 15 | 290694175 |
| 16 | 1301823805 |
| 17 | 5863740425 |
| 18 | 26550162371 |
| 19 | 120780915859 |
| 20 | 551812209781 |
| 21 | 2530915409480 |
| 22 | 11649789216869 |
| 23 | 53800623112057 |
| 24 | 249215824027266 |
| 25 | 1157671306509836 |
| 26 | 5391739956937891 |
| 27 | 25172642088618386 |
[1,1,4,12,44,160,630,2505,10274,42813,181411, 778323,3376953,14792252,65335900,290694175, 1301823805,5863740425,26550162371,120780915859, 551812209781,2530915409480,11649789216869, 53800623112057,249215824027266,1157671306509836, 5391739956937891,25172642088618386] |