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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 11 |
| 4 | 40 |
| 5 | 124 |
| 6 | 474 |
| 7 | 1599 |
| 8 | 6214 |
| 9 | 21790 |
| 10 | 85368 |
| 11 | 306948 |
| 12 | 1209606 |
| 13 | 4426724 |
| 14 | 17512502 |
| 15 | 64916857 |
| 16 | 257475442 |
| 17 | 963710264 |
| 18 | 3829460462 |
| 19 | 14442356656 |
| 20 | 57468053150 |
| 21 | 218058093974 |
| 22 | 868578080482 |
| 23 | 3312203437546 |
| 24 | 13203816362654 |
| 25 | 50560048999552 |
| 26 | 201677765851598 |
| 27 | 774971022480474 |
| 28 | 3092771736311868 |
[1,1,4,11,40,124,474,1599,6214,21790,85368,306948, 1209606,4426724,17512502,64916857,257475442, 963710264,3829460462,14442356656,57468053150, 218058093974,868578080482,3312203437546, 13203816362654,50560048999552,201677765851598, 774971022480474,3092771736311868] |