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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 9 |
| 6 | 21 |
| 7 | 52 |
| 8 | 135 |
| 9 | 368 |
| 10 | 1045 |
| 11 | 3068 |
| 12 | 9230 |
| 13 | 28245 |
| 14 | 87414 |
| 15 | 272544 |
| 16 | 854012 |
| 17 | 2685897 |
| 18 | 8473107 |
| 19 | 26805994 |
| 20 | 85045674 |
| 21 | 270599945 |
| 22 | 863529480 |
| 23 | 2763745020 |
| 24 | 8870777955 |
| 25 | 28550721966 |
| 26 | 92128996782 |
| 27 | 298004209496 |
| 28 | 966085311052 |
[0,1,1,2,4,9,21,52,135,368,1045,3068,9230,28245, 87414,272544,854012,2685897,8473107,26805994, 85045674,270599945,863529480,2763745020, 8870777955,28550721966,92128996782,298004209496, 966085311052] |