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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 14 |
| 3 | 75 |
| 4 | 429 |
| 5 | 2548 |
| 6 | 15504 |
| 7 | 95931 |
| 8 | 600875 |
| 9 | 3798795 |
| 10 | 24192090 |
| 11 | 154969620 |
| 12 | 997490844 |
| 13 | 6446369400 |
| 14 | 41802112192 |
| 15 | 271861216539 |
| 16 | 1772528290407 |
| 17 | 11582393855305 |
| 18 | 75831424919250 |
| 19 | 497337483739635 |
| 20 | 3266814940064445 |
[1,3,14,75,429,2548,15504,95931,600875,3798795, 24192090,154969620,997490844,6446369400, 41802112192,271861216539,1772528290407, 11582393855305,75831424919250,497337483739635, 3266814940064445] |