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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 1 |
| 7 | 8 |
| 8 | 68 |
| 9 | 480 |
| 10 | 3637 |
| 11 | 27968 |
| 12 | 231410 |
| 13 | 2014784 |
| 14 | 18789010 |
| 15 | 185234176 |
| 16 | 1943243785 |
| 17 | 21501237248 |
| 18 | 251589065328 |
| 19 | 3093350098432 |
| 20 | 40007001803593 |
| 21 | 541652523341824 |
| 22 | 7679190979467688 |
| 23 | 113578314941202432 |
[1,1,0,0,0,0,1,8,68,480,3637,27968,231410,2014784, 18789010,185234176,1943243785,21501237248, 251589065328,3093350098432,40007001803593, 541652523341824,7679190979467688, 113578314941202432] |