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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 6 |
| 5 | 35 |
| 6 | 217 |
| 7 | 1568 |
| 8 | 12848 |
| 9 | 117738 |
| 10 | 1194019 |
| 11 | 13282346 |
| 12 | 160856190 |
| 13 | 2107154067 |
| 14 | 29691159876 |
| 15 | 447836111629 |
| 16 | 7199765822643 |
| 17 | 122909558878512 |
| 18 | 2220556571338744 |
| 19 | 42329227454294820 |
| 20 | 849072524072460101 |
| 21 | 17877662074795269964 |
| 22 | 394248958294191005180 |
[1,0,0,1,6,35,217,1568,12848,117738,1194019, 13282346,160856190,2107154067,29691159876, 447836111629,7199765822643,122909558878512, 2220556571338744,42329227454294820, 849072524072460101,17877662074795269964, 394248958294191005180] |