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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 4 |
| 6 | 24 |
| 7 | 96 |
| 8 | 412 |
| 9 | 1607 |
| 10 | 6348 |
| 11 | 24580 |
| 12 | 96334 |
| 13 | 378569 |
| 14 | 1508220 |
| 15 | 6079720 |
| 16 | 24879878 |
| 17 | 103335386 |
| 18 | 436032901 |
| 19 | 1869019800 |
| 20 | 8139613977 |
| 21 | 36008825317 |
| 22 | 161794412893 |
| 23 | 738167013847 |
| 24 | 3418757243139 |
| 25 | 16068569129711 |
| 26 | 76622168743677 |
| 27 | 370571105669576 |
| 28 | 1817199912384794 |
[1,0,0,0,1,4,24,96,412,1607,6348,24580,96334, 378569,1508220,6079720,24879878,103335386, 436032901,1869019800,8139613977,36008825317, 161794412893,738167013847,3418757243139, 16068569129711,76622168743677,370571105669576, 1817199912384794] |