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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 1 |
| 7 | 6 |
| 8 | 44 |
| 9 | 208 |
| 10 | 912 |
| 11 | 8016 |
| 12 | 61952 |
| 13 | 671248 |
| 14 | 8160620 |
| 15 | 87412258 |
| 16 | 888954284 |
| 17 | 12156253488 |
| 18 | 180955852060 |
| 19 | 2907927356451 |
| 20 | 50317255621843 |
| 21 | 802326797235038 |
| 22 | 12251146829850324 |
| 23 | 233309934271940028 |
| 24 | 4243527581615332664 |
| 25 | 79533825261873435894 |
| 26 | 1602629887788636447221 |
| 27 | 30450585799991840921483 |
| 28 | 622433536382831426225696 |
| 29 | 14891218890120375419560713 |
| 30 | 344515231090957672408413959 |
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