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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 8 |
| 6 | 20 |
| 7 | 57 |
| 8 | 171 |
| 9 | 548 |
| 10 | 1894 |
| 11 | 6998 |
| 12 | 27368 |
| 13 | 112653 |
| 14 | 486645 |
| 15 | 2201162 |
| 16 | 10397944 |
| 17 | 51161168 |
| 18 | 261571460 |
| 19 | 1386846249 |
| 20 | 7612315023 |
| 21 | 43190917004 |
| 22 | 252951090586 |
| 23 | 1527112817054 |
| 24 | 9492126182336 |
| 25 | 60677428545165 |
| 26 | 398489257136529 |
| 27 | 2686088269505042 |
| 28 | 18567557376240748 |
[1,1,1,2,4,8,20,57,171,548,1894,6998,27368,112653, 486645,2201162,10397944,51161168,261571460, 1386846249,7612315023,43190917004,252951090586, 1527112817054,9492126182336,60677428545165, 398489257136529,2686088269505042, 18567557376240748] |