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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 60 |
| 5 | 580 |
| 6 | 7380 |
| 7 | 119700 |
| 8 | 2387280 |
| 9 | 57211056 |
| 10 | 1615703040 |
| 11 | 52950688560 |
| 12 | 1988213895360 |
| 13 | 84622184412480 |
| 14 | 4045503794492160 |
| 15 | 215531680987022400 |
| 16 | 12709328457015590400 |
| 17 | 824497514996060505600 |
| 18 | 58531734588587835294720 |
| 19 | 4525412571041289046479360 |
| 20 | 379428698362674642409728000 |
| 21 | 34365923697307101211784908800 |
| 22 | 3350637193653655199937586944000 |
[1,1,2,9,60,580,7380,119700,2387280,57211056, 1615703040,52950688560,1988213895360, 84622184412480,4045503794492160, 215531680987022400,12709328457015590400, 824497514996060505600,58531734588587835294720, 4525412571041289046479360, 379428698362674642409728000, 34365923697307101211784908800, 3350637193653655199937586944000] |