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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 4 |
| 3 | 24 |
| 4 | 160 |
| 5 | 1120 |
| 6 | 8064 |
| 7 | 59136 |
| 8 | 439296 |
| 9 | 3294720 |
| 10 | 24893440 |
| 11 | 189190144 |
| 12 | 1444724736 |
| 13 | 11076222976 |
| 14 | 85201715200 |
| 15 | 657270374400 |
| 16 | 5082890895360 |
| 17 | 39392404439040 |
| 18 | 305870434467840 |
| 19 | 2378992268083200 |
| 20 | 18531097667174400 |
| 21 | 144542561803960320 |
| 22 | 1128808577897594880 |
[0,4,24,160,1120,8064,59136,439296,3294720, 24893440,189190144,1444724736,11076222976, 85201715200,657270374400,5082890895360, 39392404439040,305870434467840,2378992268083200, 18531097667174400,144542561803960320, 1128808577897594880] |