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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 18 |
| 4 | 54 |
| 5 | 162 |
| 6 | 486 |
| 7 | 1458 |
| 8 | 4374 |
| 9 | 13122 |
| 10 | 39366 |
| 11 | 118098 |
| 12 | 354294 |
| 13 | 1062882 |
| 14 | 3188646 |
| 15 | 9565938 |
| 16 | 28697814 |
| 17 | 86093442 |
| 18 | 258280326 |
| 19 | 774840978 |
| 20 | 2324522934 |
| 21 | 6973568802 |
| 22 | 20920706406 |
| 23 | 62762119218 |
| 24 | 188286357654 |
| 25 | 564859072962 |
| 26 | 1694577218886 |
| 27 | 5083731656658 |
| 28 | 15251194969974 |
[1,2,6,18,54,162,486,1458,4374,13122,39366,118098, 354294,1062882,3188646,9565938,28697814,86093442, 258280326,774840978,2324522934,6973568802, 20920706406,62762119218,188286357654,564859072962, 1694577218886,5083731656658,15251194969974] |