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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 18 |
| 5 | 59 |
| 6 | 210 |
| 7 | 767 |
| 8 | 2901 |
| 9 | 11295 |
| 10 | 44756 |
| 11 | 180348 |
| 12 | 738130 |
| 13 | 3057350 |
| 14 | 12789793 |
| 15 | 54032745 |
| 16 | 230170481 |
| 17 | 987155382 |
| 18 | 4262047055 |
| 19 | 18511560553 |
| 20 | 80808289797 |
| 21 | 354440593530 |
| 22 | 1561601787236 |
| 23 | 6907093680245 |
| 24 | 30660957686730 |
| 25 | 136574647572439 |
| 26 | 610247973013998 |
| 27 | 2734489839406472 |
| 28 | 12286433733748477 |
[1,1,2,6,18,59,210,767,2901,11295,44756,180348, 738130,3057350,12789793,54032745,230170481, 987155382,4262047055,18511560553,80808289797, 354440593530,1561601787236,6907093680245, 30660957686730,136574647572439,610247973013998, 2734489839406472,12286433733748477] |