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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 3 |
| 3 | 60 |
| 4 | 650 |
| 5 | 5352 |
| 6 | 37681 |
| 7 | 239752 |
| 8 | 1421226 |
| 9 | 7996160 |
| 10 | 43219990 |
| 11 | 226309800 |
| 12 | 1154900708 |
| 13 | 5769562736 |
| 14 | 28312118565 |
| 15 | 136830224464 |
| 16 | 652656300122 |
| 17 | 3077631550512 |
| 18 | 14367512295274 |
| 19 | 66478236840680 |
| 20 | 305161336656876 |
| 21 | 1390869368495728 |
| 22 | 6298727501142218 |
| 23 | 28358908010334960 |
[0,3,60,650,5352,37681,239752,1421226,7996160, 43219990,226309800,1154900708,5769562736, 28312118565,136830224464,652656300122, 3077631550512,14367512295274,66478236840680, 305161336656876,1390869368495728,6298727501142218, 28358908010334960] |