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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 16 |
| 5 | 135 |
| 6 | 1246 |
| 7 | 14238 |
| 8 | 192613 |
| 9 | 2948025 |
| 10 | 51071236 |
| 11 | 985911003 |
| 12 | 20952667660 |
| 13 | 486857940660 |
| 14 | 12275673296251 |
| 15 | 333786662478363 |
| 16 | 9737819506544272 |
| 17 | 303399477464036175 |
| 18 | 10054949172135522106 |
| 19 | 353197317869395005258 |
| 20 | 13108298181041284002769 |
[1,0,1,3,16,135,1246,14238,192613,2948025, 51071236,985911003,20952667660,486857940660, 12275673296251,333786662478363,9737819506544272, 303399477464036175,10054949172135522106, 353197317869395005258,13108298181041284002769] |