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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 62 |
| 5 | 194 |
| 6 | 612 |
| 7 | 1922 |
| 8 | 6038 |
| 9 | 18980 |
| 10 | 59646 |
| 11 | 187442 |
| 12 | 589076 |
| 13 | 1851266 |
| 14 | 5817894 |
| 15 | 18283700 |
| 16 | 57459518 |
| 17 | 180575906 |
| 18 | 567489348 |
| 19 | 1783428098 |
| 20 | 5604714422 |
| 21 | 17613731780 |
| 22 | 55354032894 |
| 23 | 173959101458 |
| 24 | 546694927604 |
| 25 | 1718078222594 |
| 26 | 5399341807686 |
| 27 | 16968314698580 |
[1,2,6,20,62,194,612,1922,6038,18980,59646,187442, 589076,1851266,5817894,18283700,57459518, 180575906,567489348,1783428098,5604714422, 17613731780,55354032894,173959101458,546694927604, 1718078222594,5399341807686,16968314698580] |