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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 17 |
| 6 | 92 |
| 7 | 587 |
| 8 | 4324 |
| 9 | 36162 |
| 10 | 338611 |
| 11 | 3509239 |
| 12 | 39877720 |
| 13 | 493033635 |
| 14 | 6588722213 |
| 15 | 94638009964 |
| 16 | 1453983971265 |
| 17 | 23792464984330 |
| 18 | 413123710182463 |
| 19 | 7586453586987049 |
| 20 | 146901328548021943 |
| 21 | 2991445235886992290 |
[1,0,0,1,4,17,92,587,4324,36162,338611,3509239, 39877720,493033635,6588722213,94638009964, 1453983971265,23792464984330,413123710182463, 7586453586987049,146901328548021943, 2991445235886992290] |