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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 75 |
| 5 | 286 |
| 6 | 1150 |
| 7 | 4676 |
| 8 | 19516 |
| 9 | 82325 |
| 10 | 352551 |
| 11 | 1523146 |
| 12 | 6642454 |
| 13 | 29173778 |
| 14 | 128957103 |
| 15 | 573244772 |
| 16 | 2560570574 |
| 17 | 11488400595 |
| 18 | 51743747415 |
| 19 | 233877257170 |
| 20 | 1060458726444 |
| 21 | 4822197619857 |
| 22 | 21985847689686 |
| 23 | 100479988520140 |
| 24 | 460236805646737 |
| 25 | 2112349827532275 |
| 26 | 9713396499616699 |
| 27 | 44744248639000013 |
[1,2,6,20,75,286,1150,4676,19516,82325,352551, 1523146,6642454,29173778,128957103,573244772, 2560570574,11488400595,51743747415,233877257170, 1060458726444,4822197619857,21985847689686, 100479988520140,460236805646737,2112349827532275, 9713396499616699,44744248639000013] |