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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 7 |
| 3 | 40 |
| 4 | 234 |
| 5 | 1432 |
| 6 | 9078 |
| 7 | 59113 |
| 8 | 393125 |
| 9 | 2659233 |
| 10 | 18240801 |
| 11 | 126588424 |
| 12 | 887221916 |
| 13 | 6271153060 |
| 14 | 44652824248 |
| 15 | 319990906290 |
| 16 | 2306133322704 |
| 17 | 16703784324239 |
| 18 | 121534039921585 |
| 19 | 887845073567240 |
| 20 | 6509750423778460 |
| 21 | 47888814944642434 |
| 22 | 353362258550740732 |
[1,1,7,40,234,1432,9078,59113,393125,2659233, 18240801,126588424,887221916,6271153060, 44652824248,319990906290,2306133322704, 16703784324239,121534039921585,887845073567240, 6509750423778460,47888814944642434, 353362258550740732] |