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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 5 |
| 2 | 20 |
| 3 | 52 |
| 4 | 236 |
| 5 | 916 |
| 6 | 4060 |
| 7 | 16904 |
| 8 | 66660 |
| 9 | 265800 |
| 10 | 1059724 |
| 11 | 4219684 |
| 12 | 16816424 |
| 13 | 67131892 |
| 14 | 268216416 |
| 15 | 1072151796 |
[1,5,20,52,236,916,4060,16904,66660,265800, 1059724,4219684,16816424,67131892,268216416, 1072151796] |