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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 9 |
| 3 | 31 |
| 4 | 109 |
| 5 | 339 |
| 6 | 1043 |
| 7 | 2998 |
| 8 | 8406 |
| 9 | 22652 |
| 10 | 59521 |
| 11 | 151958 |
| 12 | 379693 |
| 13 | 927622 |
| 14 | 2224235 |
| 15 | 5236586 |
| 16 | 12130780 |
| 17 | 27669593 |
| 18 | 62229990 |
| 19 | 138095696 |
| 20 | 302673029 |
| 21 | 655627975 |
| 22 | 1404599867 |
| 23 | 2977831389 |
| 24 | 6251060785 |
| 25 | 12999299705 |
| 26 | 26791990052 |
| 27 | 54750235190 |
| 28 | 110977389012 |
[1,2,9,31,109,339,1043,2998,8406,22652,59521, 151958,379693,927622,2224235,5236586,12130780, 27669593,62229990,138095696,302673029,655627975, 1404599867,2977831389,6251060785,12999299705, 26791990052,54750235190,110977389012] |