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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 11 |
| 4 | 38 |
| 5 | 116 |
| 6 | 440 |
| 7 | 1453 |
| 8 | 5530 |
| 9 | 18794 |
| 10 | 72792 |
| 11 | 257238 |
| 12 | 992644 |
| 13 | 3549594 |
| 14 | 13853496 |
| 15 | 50447453 |
| 16 | 196718714 |
| 17 | 721500978 |
| 18 | 2829371848 |
| 19 | 10503154516 |
| 20 | 41147601932 |
| 21 | 153417689174 |
| 22 | 603530012488 |
| 23 | 2267966093122 |
| 24 | 8917294536916 |
| 25 | 33615803655530 |
| 26 | 132535696401192 |
| 27 | 502544406495538 |
| 28 | 1980452388616776 |
[1,1,4,11,38,116,440,1453,5530,18794,72792,257238, 992644,3549594,13853496,50447453,196718714, 721500978,2829371848,10503154516,41147601932, 153417689174,603530012488,2267966093122, 8917294536916,33615803655530,132535696401192, 502544406495538,1980452388616776] |