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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 60 |
| 4 | 18336 |
| 5 | 840800 |
| 6 | 14629200 |
| 7 | 143939460 |
| 8 | 971877760 |
| 9 | 5018582016 |
| 10 | 21193207200 |
| 11 | 76518984300 |
| 12 | 243664127520 |
| 13 | 699965254560 |
| 14 | 1844973808496 |
| 15 | 4520720267700 |
| 16 | 10403885452800 |
| 17 | 22674321863680 |
| 18 | 47112768624960 |
| 19 | 93845538165276 |
| 20 | 180039346960800 |
| 21 | 333959821087200 |
| 22 | 600947653207440 |
[0,0,60,18336,840800,14629200,143939460,971877760, 5018582016,21193207200,76518984300,243664127520, 699965254560,1844973808496,4520720267700, 10403885452800,22674321863680,47112768624960, 93845538165276,180039346960800,333959821087200, 600947653207440] |