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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 14 |
| 3 | 48 |
| 4 | 166 |
| 5 | 579 |
| 6 | 2037 |
| 7 | 7226 |
| 8 | 25831 |
| 9 | 92988 |
| 10 | 336872 |
| 11 | 1227400 |
| 12 | 4495191 |
| 13 | 16540013 |
| 14 | 61116635 |
| 15 | 226700190 |
| 16 | 843851715 |
| 17 | 3151174800 |
| 18 | 11802018060 |
| 19 | 44321634960 |
| 20 | 166863174240 |
| 21 | 629665197174 |
| 22 | 2381173300698 |
| 23 | 9022761052340 |
[1,4,14,48,166,579,2037,7226,25831,92988,336872, 1227400,4495191,16540013,61116635,226700190, 843851715,3151174800,11802018060,44321634960, 166863174240,629665197174,2381173300698, 9022761052340] |