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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 4 |
| 6 | 8 |
| 7 | 14 |
| 8 | 32 |
| 9 | 142 |
| 10 | 426 |
| 11 | 1204 |
| 12 | 3747 |
| 13 | 9374 |
| 14 | 26306 |
| 15 | 77700 |
| 16 | 219877 |
| 17 | 1169656 |
| 18 | 4736264 |
| 19 | 17360564 |
| 20 | 69631372 |
| 21 | 242754286 |
| 22 | 891384309 |
| 23 | 3412857926 |
| 24 | 12836957200 |
| 25 | 42721475348 |
| 26 | 152125749587 |
| 27 | 549831594988 |
[0,1,1,1,4,8,14,32,142,426,1204,3747,9374,26306, 77700,219877,1169656,4736264,17360564,69631372, 242754286,891384309,3412857926,12836957200, 42721475348,152125749587,549831594988] |