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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 32 |
| 5 | 480 |
| 6 | 7880 |
| 7 | 145320 |
| 8 | 3009888 |
| 9 | 69554240 |
| 10 | 1779185360 |
| 11 | 49995179520 |
| 12 | 1532580072320 |
| 13 | 50934256044672 |
| 14 | 1825145974743000 |
| 15 | 70172455476381440 |
| 16 | 2882264153273207360 |
| 17 | 125985060813367664640 |
| 18 | 5840066736661562391968 |
| 19 | 286204501001426735001600 |
[0,0,0,2,32,480,7880,145320,3009888,69554240, 1779185360,49995179520,1532580072320, 50934256044672,1825145974743000,70172455476381440, 2882264153273207360,125985060813367664640, 5840066736661562391968,286204501001426735001600] |