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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 2 |
| 3 | 12 |
| 4 | 62 |
| 5 | 320 |
| 6 | 1712 |
| 7 | 9604 |
| 8 | 56674 |
| 9 | 351792 |
| 10 | 2293862 |
| 11 | 15682216 |
| 12 | 112179608 |
| 13 | 837905016 |
| 14 | 6522165834 |
| 15 | 52807401908 |
| 16 | 443962338894 |
| 17 | 3869376656384 |
| 18 | 34908008426360 |
| 19 | 325530083655692 |
| 20 | 3133830448212442 |
| 21 | 31106728455899128 |
| 22 | 318009567467999574 |
| 23 | 3344865730200667832 |
| 24 | 36161434396223563504 |
[0,0,2,12,62,320,1712,9604,56674,351792,2293862, 15682216,112179608,837905016,6522165834, 52807401908,443962338894,3869376656384, 34908008426360,325530083655692,3133830448212442, 31106728455899128,318009567467999574, 3344865730200667832,36161434396223563504] |