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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 12 |
| 2 | 180 |
| 3 | 2928 |
| 4 | 49860 |
| 5 | 875952 |
| 6 | 15754704 |
| 7 | 288722880 |
| 8 | 5373771876 |
| 9 | 101334517680 |
| 10 | 1932405892560 |
| 11 | 37208369165760 |
| 12 | 722497419680400 |
| 13 | 14132680228175040 |
| 14 | 278236490874120000 |
| 15 | 5508974545258860288 |
| 16 | 109624581377872629156 |
| 17 | 2191185332414847848880 |
| 18 | 43971545517545956240464 |
[1,12,180,2928,49860,875952,15754704,288722880, 5373771876,101334517680,1932405892560, 37208369165760,722497419680400,14132680228175040, 278236490874120000,5508974545258860288, 109624581377872629156,2191185332414847848880, 43971545517545956240464] |