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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 11 |
| 4 | 38 |
| 5 | 138 |
| 6 | 502 |
| 7 | 1865 |
| 8 | 7224 |
| 9 | 28050 |
| 10 | 111038 |
| 11 | 443212 |
| 12 | 1776894 |
| 13 | 7204202 |
| 14 | 29425674 |
| 15 | 120737771 |
| 16 | 498100134 |
| 17 | 2061928840 |
| 18 | 8570899732 |
| 19 | 35784144922 |
| 20 | 149853702562 |
| 21 | 629300079802 |
| 22 | 2649399584968 |
| 23 | 11179870334690 |
| 24 | 47294761395830 |
| 25 | 200508019356844 |
| 26 | 851618083338054 |
| 27 | 3623315901711840 |
[1,1,4,11,38,138,502,1865,7224,28050,111038, 443212,1776894,7204202,29425674,120737771, 498100134,2061928840,8570899732,35784144922, 149853702562,629300079802,2649399584968, 11179870334690,47294761395830,200508019356844, 851618083338054,3623315901711840] |