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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 4 |
| 4 | 12 |
| 5 | 22 |
| 6 | 71 |
| 7 | 181 |
| 8 | 618 |
| 9 | 1957 |
| 10 | 6966 |
| 11 | 24367 |
| 12 | 89010 |
| 13 | 324766 |
| 14 | 1204815 |
| 15 | 4482400 |
| 16 | 16802826 |
| 17 | 63195016 |
| 18 | 238711285 |
| 19 | 904338163 |
| 20 | 3436380192 |
| 21 | 13089961012 |
| 22 | 49979421837 |
| 23 | 191221556269 |
| 24 | 733014218506 |
| 25 | 2814758323498 |
| 26 | 10825986453978 |
| 27 | 41700030726757 |
| 28 | 160842946895004 |
[1,1,3,4,12,22,71,181,618,1957,6966,24367,89010, 324766,1204815,4482400,16802826,63195016, 238711285,904338163,3436380192,13089961012, 49979421837,191221556269,733014218506, 2814758323498,10825986453978,41700030726757, 160842946895004] |