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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 90 |
| 4 | 2520 |
| 5 | 16200 |
| 6 | 7484400 |
| 7 | 681080400 |
| 8 | 11675664000 |
| 9 | 12504636144000 |
| 10 | 2375880867360000 |
| 11 | 78404068622880000 |
| 12 | 8910391798788480000 |
| 13 | 49229914688306352000000 |
| 14 | 2658415393168543008000000 |
| 15 | 476169110129306674080000000 |
| 16 | 4015057936610313875842560000000 |
| 17 | 321778214634055154906810880000000 |
[1,1,6,90,2520,16200,7484400,681080400, 11675664000,12504636144000,2375880867360000, 78404068622880000,8910391798788480000, 49229914688306352000000,2658415393168543008000000, 476169110129306674080000000, 4015057936610313875842560000000, 321778214634055154906810880000000] |