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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 7 |
| 5 | 24 |
| 6 | 88 |
| 7 | 328 |
| 8 | 1235 |
| 9 | 4668 |
| 10 | 17675 |
| 11 | 66974 |
| 12 | 253858 |
| 13 | 962352 |
| 14 | 3648397 |
| 15 | 13831870 |
| 16 | 52440191 |
| 17 | 198815196 |
| 18 | 753764564 |
| 19 | 2857736696 |
| 20 | 10834499599 |
| 21 | 41076702120 |
| 22 | 155733594211 |
| 23 | 590430871282 |
| 24 | 2238493367822 |
| 25 | 8486772670944 |
| 26 | 32175798041273 |
[0,1,2,7,24,88,328,1235,4668,17675,66974,253858, 962352,3648397,13831870,52440191,198815196, 753764564,2857736696,10834499599,41076702120, 155733594211,590430871282,2238493367822, 8486772670944,32175798041273] |