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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 69 |
| 5 | 420 |
| 6 | 2845 |
| 7 | 21187 |
| 8 | 173554 |
| 9 | 1584768 |
| 10 | 16617329 |
| 11 | 210472915 |
| 12 | 3451735696 |
| 13 | 78546037008 |
| 14 | 2582920450824 |
| 15 | 123477535651607 |
| 16 | 8494578276132389 |
| 17 | 832041256283517038 |
| 18 | 115176854055075767837 |
| 19 | 22420312200544123743720 |
[1,1,3,13,69,420,2845,21187,173554,1584768, 16617329,210472915,3451735696,78546037008, 2582920450824,123477535651607,8494578276132389, 832041256283517038,115176854055075767837, 22420312200544123743720] |