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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 14 |
| 4 | 102 |
| 5 | 1032 |
| 6 | 12840 |
| 7 | 194400 |
| 8 | 3457440 |
| 9 | 70680960 |
| 10 | 1635863040 |
| 11 | 42293664000 |
| 12 | 1208201702400 |
| 13 | 37796100249600 |
| 14 | 1285064055475200 |
| 15 | 47183768081049600 |
| 16 | 1860676781483520000 |
| 17 | 78432007085752320000 |
| 18 | 3519255355814854656000 |
[1,3,14,102,1032,12840,194400,3457440,70680960, 1635863040,42293664000,1208201702400, 37796100249600,1285064055475200,47183768081049600, 1860676781483520000,78432007085752320000, 3519255355814854656000] |