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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 11 |
| 4 | 40 |
| 5 | 161 |
| 6 | 668 |
| 7 | 2836 |
| 8 | 12375 |
| 9 | 54900 |
| 10 | 247280 |
| 11 | 1125020 |
| 12 | 5172670 |
| 13 | 23971303 |
| 14 | 111796965 |
| 15 | 524564578 |
| 16 | 2473888979 |
| 17 | 11717814258 |
| 18 | 55713194024 |
| 19 | 265828035935 |
| 20 | 1272204602838 |
| 21 | 6104857054877 |
| 22 | 29367359951719 |
| 23 | 141586007793508 |
| 24 | 683967387118882 |
| 25 | 3310060952570425 |
| 26 | 16045866486100742 |
| 27 | 77901869473238047 |
[1,1,3,11,40,161,668,2836,12375,54900,247280, 1125020,5172670,23971303,111796965,524564578, 2473888979,11717814258,55713194024,265828035935, 1272204602838,6104857054877,29367359951719, 141586007793508,683967387118882,3310060952570425, 16045866486100742,77901869473238047] |