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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 21 |
| 6 | 52 |
| 7 | 134 |
| 8 | 361 |
| 9 | 1009 |
| 10 | 2926 |
| 11 | 8768 |
| 12 | 27121 |
| 13 | 86373 |
| 14 | 282864 |
| 15 | 950866 |
| 16 | 3277169 |
| 17 | 11564353 |
| 18 | 41739130 |
| 19 | 153919324 |
| 20 | 579411641 |
| 21 | 2224535125 |
| 22 | 8703993420 |
| 23 | 34681783422 |
| 24 | 140637608089 |
| 25 | 580019801201 |
| 26 | 2431509498406 |
| 27 | 10355296410712 |
[1,1,2,4,9,21,52,134,361,1009,2926,8768,27121, 86373,282864,950866,3277169,11564353,41739130, 153919324,579411641,2224535125,8703993420, 34681783422,140637608089,580019801201, 2431509498406,10355296410712] |