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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 2 |
| 6 | 9 |
| 7 | 28 |
| 8 | 144 |
| 9 | 640 |
| 10 | 2348 |
| 11 | 6740 |
| 12 | 37161 |
| 13 | 208186 |
| 14 | 1410137 |
| 15 | 8322892 |
| 16 | 47973920 |
| 17 | 231922220 |
| 18 | 1747678465 |
| 19 | 11712495736 |
| 20 | 101585559496 |
| 21 | 776251710048 |
| 22 | 6154289307912 |
| 23 | 41248110305520 |
| 24 | 397850617247393 |
[1,0,0,0,1,2,9,28,144,640,2348,6740,37161,208186, 1410137,8322892,47973920,231922220,1747678465, 11712495736,101585559496,776251710048, 6154289307912,41248110305520,397850617247393] |