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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 8 |
| 5 | 37 |
| 6 | 248 |
| 7 | 1749 |
| 8 | 14284 |
| 9 | 130343 |
| 10 | 1318194 |
| 11 | 14630853 |
| 12 | 176881314 |
| 13 | 2313878809 |
| 14 | 32567413038 |
| 15 | 490762544907 |
| 16 | 7883735348152 |
| 17 | 134496767915753 |
| 18 | 2428518101193448 |
| 19 | 46270707955530689 |
| 20 | 927734890186657436 |
[0,0,1,1,8,37,248,1749,14284,130343,1318194, 14630853,176881314,2313878809,32567413038, 490762544907,7883735348152,134496767915753, 2428518101193448,46270707955530689, 927734890186657436] |