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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 8 |
| 4 | 23 |
| 5 | 64 |
| 6 | 197 |
| 7 | 588 |
| 8 | 1806 |
| 9 | 5509 |
| 10 | 16677 |
| 11 | 49505 |
| 12 | 143761 |
| 13 | 406091 |
| 14 | 1114890 |
| 15 | 2970964 |
| 16 | 7685972 |
| 17 | 19311709 |
| 18 | 47170674 |
| 19 | 112123118 |
| 20 | 259662333 |
| 21 | 586583731 |
| 22 | 1294143065 |
| 23 | 2791716176 |
| 24 | 5895027869 |
| 25 | 12198014683 |
| 26 | 24758285639 |
| 27 | 49339306519 |
[1,1,3,8,23,64,197,588,1806,5509,16677,49505, 143761,406091,1114890,2970964,7685972,19311709, 47170674,112123118,259662333,586583731,1294143065, 2791716176,5895027869,12198014683,24758285639, 49339306519] |