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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 11 |
| 6 | 33 |
| 7 | 103 |
| 8 | 330 |
| 9 | 1077 |
| 10 | 3556 |
| 11 | 11895 |
| 12 | 40187 |
| 13 | 137049 |
| 14 | 471070 |
| 15 | 1630819 |
| 16 | 5680854 |
| 17 | 19899698 |
| 18 | 70053093 |
| 19 | 247711242 |
| 20 | 879441789 |
| 21 | 3133648932 |
| 22 | 11202930544 |
| 23 | 40172365842 |
| 24 | 144453506494 |
| 25 | 520759972064 |
| 26 | 1881787195944 |
| 27 | 6814766134276 |
[1,1,1,2,4,11,33,103,330,1077,3556,11895,40187, 137049,471070,1630819,5680854,19899698,70053093, 247711242,879441789,3133648932,11202930544, 40172365842,144453506494,520759972064, 1881787195944,6814766134276] |