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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 2 |
| 3 | 8 |
| 4 | 40 |
| 5 | 208 |
| 6 | 1408 |
| 7 | 12224 |
| 8 | 157312 |
| 9 | 3478528 |
| 10 | 147761664 |
| 11 | 12592434176 |
| 12 | 2112188653568 |
| 13 | 680441850810368 |
| 14 | 415073848421801984 |
| 15 | 476853486273606582272 |
| 16 | 1030736815796444156755968 |
| 17 | 4196432048875514376435007488 |
| 18 | 32243698461915435195120257335296 |
[0,0,2,8,40,208,1408,12224,157312,3478528, 147761664,12592434176,2112188653568, 680441850810368,415073848421801984, 476853486273606582272,1030736815796444156755968, 4196432048875514376435007488, 32243698461915435195120257335296] |