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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 1 |
| 4 | 1 |
| 5 | 6 |
| 6 | 17 |
| 7 | 60 |
| 8 | 201 |
| 9 | 688 |
| 10 | 2370 |
| 11 | 8218 |
| 12 | 28703 |
| 13 | 100846 |
| 14 | 356370 |
| 15 | 1265918 |
| 16 | 4518571 |
| 17 | 16200070 |
| 18 | 58317298 |
| 19 | 210718174 |
| 20 | 764015412 |
| 21 | 2778955460 |
| 22 | 10137598506 |
| 23 | 37082361204 |
| 24 | 135985402371 |
| 25 | 499840932062 |
| 26 | 1841260760276 |
| 27 | 6796395432602 |
| 28 | 25134116857096 |
[1,2,1,1,6,17,60,201,688,2370,8218,28703,100846, 356370,1265918,4518571,16200070,58317298, 210718174,764015412,2778955460,10137598506, 37082361204,135985402371,499840932062, 1841260760276,6796395432602,25134116857096] |