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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 8 |
| 4 | 23 |
| 5 | 54 |
| 6 | 143 |
| 7 | 354 |
| 8 | 914 |
| 9 | 2306 |
| 10 | 5907 |
| 11 | 15012 |
| 12 | 38368 |
| 13 | 97804 |
| 14 | 249865 |
| 15 | 637834 |
| 16 | 1629729 |
| 17 | 4163398 |
| 18 | 10640753 |
| 19 | 27196246 |
| 20 | 69526562 |
| 21 | 177757762 |
| 22 | 454541197 |
| 23 | 1162403180 |
| 24 | 2972953385 |
| 25 | 7604223184 |
| 26 | 19451741733 |
| 27 | 49761433640 |
| 28 | 127308417226 |
[1,1,4,8,23,54,143,354,914,2306,5907,15012,38368, 97804,249865,637834,1629729,4163398,10640753, 27196246,69526562,177757762,454541197,1162403180, 2972953385,7604223184,19451741733,49761433640, 127308417226] |