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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 17 |
| 5 | 50 |
| 6 | 148 |
| 7 | 441 |
| 8 | 1318 |
| 9 | 3946 |
| 10 | 11825 |
| 11 | 35454 |
| 12 | 106328 |
| 13 | 318929 |
| 14 | 956698 |
| 15 | 2869950 |
| 16 | 8609617 |
| 17 | 25828474 |
| 18 | 77484812 |
| 19 | 232453449 |
| 20 | 697358750 |
| 21 | 2092073666 |
| 22 | 6276216817 |
| 23 | 18828643686 |
| 24 | 56485920112 |
| 25 | 169457742625 |
| 26 | 508373199218 |
| 27 | 1525119551286 |
[0,1,2,6,17,50,148,441,1318,3946,11825,35454, 106328,318929,956698,2869950,8609617,25828474, 77484812,232453449,697358750,2092073666, 6276216817,18828643686,56485920112,169457742625, 508373199218,1525119551286] |