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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 24 |
| 3 | 540 |
| 4 | 12040 |
| 5 | 258300 |
| 6 | 5258484 |
| 7 | 102834732 |
| 8 | 1948929840 |
| 9 | 36099037260 |
| 10 | 656717973340 |
| 11 | 11782163004612 |
| 12 | 208991112900024 |
| 13 | 3673025551895700 |
| 14 | 64051241252342400 |
| 15 | 1109647124772841800 |
| 16 | 19114937411113617120 |
| 17 | 327669959548309223340 |
| 18 | 5592728044559732561100 |
[0,24,540,12040,258300,5258484,102834732, 1948929840,36099037260,656717973340, 11782163004612,208991112900024,3673025551895700, 64051241252342400,1109647124772841800, 19114937411113617120,327669959548309223340, 5592728044559732561100] |