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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 19 |
| 4 | 60 |
| 5 | 185 |
| 6 | 559 |
| 7 | 1662 |
| 8 | 4875 |
| 9 | 14134 |
| 10 | 40564 |
| 11 | 115370 |
| 12 | 325465 |
| 13 | 911355 |
| 14 | 2534595 |
| 15 | 7004827 |
| 16 | 19246626 |
| 17 | 52596377 |
| 18 | 143006632 |
| 19 | 386984573 |
| 20 | 1042537831 |
| 21 | 2796803110 |
| 22 | 7473161196 |
| 23 | 19893461042 |
| 24 | 52767059608 |
| 25 | 139488323734 |
| 26 | 367540167625 |
| 27 | 965445514862 |
| 28 | 2528516552660 |
[1,2,6,19,60,185,559,1662,4875,14134,40564,115370, 325465,911355,2534595,7004827,19246626,52596377, 143006632,386984573,1042537831,2796803110, 7473161196,19893461042,52767059608,139488323734, 367540167625,965445514862,2528516552660] |