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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 8 |
| 4 | 26 |
| 5 | 84 |
| 6 | 272 |
| 7 | 882 |
| 8 | 2862 |
| 9 | 9290 |
| 10 | 30160 |
| 11 | 97922 |
| 12 | 317940 |
| 13 | 1032328 |
| 14 | 3351922 |
| 15 | 10883582 |
| 16 | 35338706 |
| 17 | 114743960 |
| 18 | 372571146 |
| 19 | 1209730676 |
| 20 | 3927970464 |
| 21 | 12754039410 |
| 22 | 41412104942 |
| 23 | 134464258714 |
| 24 | 436602703328 |
| 25 | 1417640069298 |
| 26 | 4603048385236 |
[0,2,8,26,84,272,882,2862,9290,30160,97922,317940, 1032328,3351922,10883582,35338706,114743960, 372571146,1209730676,3927970464,12754039410, 41412104942,134464258714,436602703328, 1417640069298,4603048385236] |