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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 16 |
| 4 | 56 |
| 5 | 176 |
| 6 | 576 |
| 7 | 1856 |
| 8 | 6016 |
| 9 | 19456 |
| 10 | 62976 |
| 11 | 203776 |
| 12 | 659456 |
| 13 | 2134016 |
| 14 | 6905856 |
| 15 | 22347776 |
| 16 | 72318976 |
| 17 | 234029056 |
| 18 | 757334016 |
| 19 | 2450784256 |
| 20 | 7930904576 |
| 21 | 25664946176 |
| 22 | 83053510656 |
| 23 | 268766806016 |
| 24 | 869747654656 |
| 25 | 2814562533376 |
| 26 | 9108115685376 |
| 27 | 29474481504256 |
[1,1,6,16,56,176,576,1856,6016,19456,62976,203776, 659456,2134016,6905856,22347776,72318976, 234029056,757334016,2450784256,7930904576, 25664946176,83053510656,268766806016,869747654656, 2814562533376,9108115685376,29474481504256] |