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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 66 |
| 4 | 172 |
| 5 | 4310 |
| 6 | 12732 |
| 7 | 280084 |
| 8 | 894872 |
| 9 | 18149094 |
| 10 | 61304940 |
| 11 | 1173803004 |
| 12 | 4136934888 |
| 13 | 75812881404 |
| 14 | 276427353048 |
| 15 | 4891514031720 |
| 16 | 18343552465968 |
| 17 | 315349842088326 |
| 18 | 1211087339244108 |
| 19 | 20316955153568876 |
| 20 | 79648216569893320 |
| 21 | 1308249951485397396 |
[0,1,2,66,172,4310,12732,280084,894872,18149094, 61304940,1173803004,4136934888,75812881404, 276427353048,4891514031720,18343552465968, 315349842088326,1211087339244108, 20316955153568876,79648216569893320, 1308249951485397396] |