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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 4 |
| 2 | 8 |
| 3 | 15 |
| 4 | 42 |
| 5 | 127 |
| 6 | 376 |
| 7 | 1122 |
| 8 | 3344 |
| 9 | 9980 |
| 10 | 29796 |
| 11 | 89007 |
| 12 | 265986 |
| 13 | 795147 |
| 14 | 2377744 |
| 15 | 7112065 |
| 16 | 21277698 |
| 17 | 63670773 |
| 18 | 190560180 |
| 19 | 570416805 |
| 20 | 1707707142 |
| 21 | 5113158165 |
| 22 | 15311384784 |
| 23 | 45854766744 |
| 24 | 137339426436 |
| 25 | 411379964442 |
| 26 | 1232324471060 |
[2,4,8,15,42,127,376,1122,3344,9980,29796,89007, 265986,795147,2377744,7112065,21277698,63670773, 190560180,570416805,1707707142,5113158165, 15311384784,45854766744,137339426436,411379964442, 1232324471060] |