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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 0 |
| 9 | 1 |
| 10 | 4 |
| 11 | 20 |
| 12 | 116 |
| 13 | 820 |
| 14 | 6600 |
| 15 | 59650 |
| 16 | 598140 |
| 17 | 6592740 |
| 18 | 79232140 |
| 19 | 1031214100 |
| 20 | 14450182880 |
| 21 | 216911207555 |
| 22 | 3472641749080 |
| 23 | 59063810100120 |
| 24 | 1063582404217144 |
| 25 | 20215010963623896 |
| 26 | 404418346892678160 |
| 27 | 8494912449554675844 |
| 28 | 186928503912130116360 |
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