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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 44 |
| 5 | 155 |
| 6 | 580 |
| 7 | 2128 |
| 8 | 8092 |
| 9 | 30276 |
| 10 | 116304 |
| 11 | 440484 |
| 12 | 1703636 |
| 13 | 6506786 |
| 14 | 25288120 |
| 15 | 97181760 |
| 16 | 379061020 |
| 17 | 1463609356 |
| 18 | 5724954544 |
| 19 | 22187304112 |
| 20 | 86981744944 |
| 21 | 338118529539 |
| 22 | 1327977811076 |
| 23 | 5175023913008 |
| 24 | 20356299454276 |
[1,1,4,12,44,155,580,2128,8092,30276,116304, 440484,1703636,6506786,25288120,97181760, 379061020,1463609356,5724954544,22187304112, 86981744944,338118529539,1327977811076, 5175023913008,20356299454276] |