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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 7 |
| 4 | 30 |
| 5 | 75 |
| 6 | 293 |
| 7 | 897 |
| 8 | 3296 |
| 9 | 11493 |
| 10 | 41905 |
| 11 | 153503 |
| 12 | 570138 |
| 13 | 2136265 |
| 14 | 8128562 |
| 15 | 30938365 |
| 16 | 119262756 |
| 17 | 461558439 |
| 18 | 1797401295 |
| 19 | 7047184967 |
| 20 | 27701702878 |
| 21 | 109512364145 |
| 22 | 434806576518 |
| 23 | 1730879700961 |
| 24 | 6923437993554 |
| 25 | 27750890786575 |
| 26 | 111617155390501 |
| 27 | 450364141890515 |
| 28 | 1820424319409176 |
[1,1,4,7,30,75,293,897,3296,11493,41905,153503, 570138,2136265,8128562,30938365,119262756, 461558439,1797401295,7047184967,27701702878, 109512364145,434806576518,1730879700961, 6923437993554,27750890786575,111617155390501, 450364141890515,1820424319409176] |