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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 10 |
| 3 | 121 |
| 4 | 1440 |
| 5 | 17161 |
| 6 | 204490 |
| 7 | 2436721 |
| 8 | 29036160 |
| 9 | 345997201 |
| 10 | 4122930250 |
| 11 | 49129165801 |
| 12 | 585427059360 |
| 13 | 6975995546521 |
| 14 | 83126519498890 |
| 15 | 990542238440161 |
| 16 | 11803380341783040 |
| 17 | 140650021862956321 |
| 18 | 1675996882013692810 |
| 19 | 19971312562301357401 |
| 20 | 237979753865602596000 |
[0,1,10,121,1440,17161,204490,2436721,29036160, 345997201,4122930250,49129165801,585427059360, 6975995546521,83126519498890,990542238440161, 11803380341783040,140650021862956321, 1675996882013692810,19971312562301357401, 237979753865602596000] |