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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 20 |
| 5 | 240 |
| 6 | 5224 |
| 7 | 209832 |
| 8 | 15956480 |
| 9 | 2346694080 |
| 10 | 675730946176 |
| 11 | 383352300553728 |
| 12 | 430056580863004160 |
| 13 | 956441558748755089920 |
| 14 | 4224552623552204307349504 |
| 15 | 37106534862502586820794145792 |
| 16 | 648740342428921612538202170408960 |
| 17 | 22591362491840723496251402052982210560 |
| 18 | 1567817841212459564387810603215973889703936 |
[1,0,1,3,20,240,5224,209832,15956480,2346694080, 675730946176,383352300553728,430056580863004160, 956441558748755089920,4224552623552204307349504, 37106534862502586820794145792, 648740342428921612538202170408960, 22591362491840723496251402052982210560, 1567817841212459564387810603215973889703936] |