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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 7 |
| 5 | 43 |
| 6 | 281 |
| 7 | 2056 |
| 8 | 17004 |
| 9 | 157809 |
| 10 | 1622515 |
| 11 | 18245335 |
| 12 | 222004597 |
| 13 | 2898508416 |
| 14 | 40343356184 |
| 15 | 595578837205 |
| 16 | 9287308741827 |
| 17 | 152459628788599 |
| 18 | 2627373030049669 |
| 19 | 47425289731038656 |
| 20 | 895098852673047772 |
| 21 | 17644305594671247141 |
| 22 | 363065584549610882703 |
| 23 | 7799894520723959486795 |
[1,0,0,1,7,43,281,2056,17004,157809,1622515, 18245335,222004597,2898508416,40343356184, 595578837205,9287308741827,152459628788599, 2627373030049669,47425289731038656, 895098852673047772,17644305594671247141, 363065584549610882703,7799894520723959486795] |