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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 49 |
| 5 | 191 |
| 6 | 815 |
| 7 | 3469 |
| 8 | 15307 |
| 9 | 68013 |
| 10 | 307268 |
| 11 | 1398768 |
| 12 | 6428729 |
| 13 | 29727505 |
| 14 | 138333374 |
| 15 | 646828034 |
| 16 | 3038128475 |
| 17 | 14323832261 |
| 18 | 67765179616 |
| 19 | 321553421700 |
| 20 | 1529953926595 |
| 21 | 7297218756599 |
| 22 | 34881425500517 |
| 23 | 167070104553465 |
| 24 | 801674006390029 |
| 25 | 3853224043493441 |
| 26 | 18548991941844770 |
| 27 | 89419945252812416 |
[1,1,4,12,49,191,815,3469,15307,68013,307268, 1398768,6428729,29727505,138333374,646828034, 3038128475,14323832261,67765179616,321553421700, 1529953926595,7297218756599,34881425500517, 167070104553465,801674006390029,3853224043493441, 18548991941844770,89419945252812416] |