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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 19 |
| 4 | 66 |
| 5 | 246 |
| 6 | 959 |
| 7 | 3821 |
| 8 | 15516 |
| 9 | 64222 |
| 10 | 269701 |
| 11 | 1147397 |
| 12 | 4920972 |
| 13 | 21274085 |
| 14 | 92683938 |
| 15 | 406473019 |
| 16 | 1792230903 |
| 17 | 7938032686 |
| 18 | 35313624670 |
| 19 | 157740457577 |
| 20 | 707180810177 |
| 21 | 3180111103615 |
| 22 | 14341410165138 |
| 23 | 64853404230235 |
| 24 | 294020538994255 |
| 25 | 1336004749977621 |
| 26 | 6083069299292362 |
| 27 | 27751482911671438 |
[1,2,6,19,66,246,959,3821,15516,64222,269701, 1147397,4920972,21274085,92683938,406473019, 1792230903,7938032686,35313624670,157740457577, 707180810177,3180111103615,14341410165138, 64853404230235,294020538994255,1336004749977621, 6083069299292362,27751482911671438] |