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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 60 |
| 6 | 362 |
| 7 | 2562 |
| 8 | 20820 |
| 9 | 191088 |
| 10 | 1955020 |
| 11 | 22061380 |
| 12 | 272197160 |
| 13 | 3645227040 |
| 14 | 52656804440 |
| 15 | 816114251400 |
| 16 | 13508168448400 |
| 17 | 237805776169600 |
| 18 | 4436759277524400 |
| 19 | 87445191383773200 |
| 20 | 1815460566861236000 |
| 21 | 39600109151685600000 |
| 22 | 905416958295793788000 |
[0,0,1,3,12,60,362,2562,20820,191088,1955020, 22061380,272197160,3645227040,52656804440, 816114251400,13508168448400,237805776169600, 4436759277524400,87445191383773200, 1815460566861236000,39600109151685600000, 905416958295793788000] |