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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 57 |
| 5 | 236 |
| 6 | 1106 |
| 7 | 5136 |
| 8 | 25112 |
| 9 | 123604 |
| 10 | 624229 |
| 11 | 3181337 |
| 12 | 16456910 |
| 13 | 85845734 |
| 14 | 452215297 |
| 15 | 2398829267 |
| 16 | 12815000375 |
| 17 | 68850087543 |
| 18 | 371908087035 |
| 19 | 2018269612417 |
| 20 | 10999942891088 |
| 21 | 60181126016328 |
| 22 | 330414426742222 |
| 23 | 1819877327401550 |
| 24 | 10053145748429452 |
| 25 | 55684213462489305 |
| 26 | 309204003830794592 |
[1,1,4,13,57,236,1106,5136,25112,123604,624229, 3181337,16456910,85845734,452215297,2398829267, 12815000375,68850087543,371908087035, 2018269612417,10999942891088,60181126016328, 330414426742222,1819877327401550, 10053145748429452,55684213462489305, 309204003830794592] |