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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 20 |
| 3 | 84 |
| 4 | 296 |
| 5 | 1124 |
| 6 | 4056 |
| 7 | 15100 |
| 8 | 55288 |
| 9 | 204740 |
| 10 | 753336 |
| 11 | 2782588 |
| 12 | 10252952 |
| 13 | 37831684 |
| 14 | 139470616 |
| 15 | 514443580 |
| 16 | 1896954168 |
| 17 | 6996160196 |
| 18 | 25799583352 |
| 19 | 95147186940 |
| 20 | 350881763288 |
| 21 | 1294007162500 |
| 22 | 4772059430872 |
| 23 | 17598637988284 |
| 24 | 64900766401656 |
| 25 | 239343741625668 |
| 26 | 882659972822840 |
| 27 | 3255107458681212 |
| 28 | 12004301666699032 |
[1,6,20,84,296,1124,4056,15100,55288,204740, 753336,2782588,10252952,37831684,139470616, 514443580,1896954168,6996160196,25799583352, 95147186940,350881763288,1294007162500, 4772059430872,17598637988284,64900766401656, 239343741625668,882659972822840,3255107458681212, 12004301666699032] |