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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 2 |
| 4 | 10 |
| 5 | 30 |
| 6 | 104 |
| 7 | 340 |
| 8 | 1144 |
| 9 | 3795 |
| 10 | 12683 |
| 11 | 42227 |
| 12 | 140876 |
| 13 | 469517 |
| 14 | 1565586 |
| 15 | 5219130 |
| 16 | 17400850 |
| 17 | 58012053 |
| 18 | 193409644 |
| 19 | 644810491 |
| 20 | 2149754855 |
| 21 | 7167115016 |
| 22 | 23894640479 |
| 23 | 79662932803 |
| 24 | 265590322328 |
| 25 | 885458314722 |
| 26 | 2952052210282 |
| 27 | 9841922224851 |
[0,2,2,10,30,104,340,1144,3795,12683,42227,140876, 469517,1565586,5219130,17400850,58012053, 193409644,644810491,2149754855,7167115016, 23894640479,79662932803,265590322328,885458314722, 2952052210282,9841922224851] |