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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 840 |
| 4 | 10080 |
| 5 | 57960 |
| 6 | 228480 |
| 7 | 710640 |
| 8 | 1874880 |
| 9 | 4379760 |
| 10 | 9313920 |
| 11 | 18378360 |
| 12 | 34114080 |
| 13 | 60180120 |
| 14 | 101687040 |
| 15 | 165590880 |
| 16 | 261152640 |
| 17 | 400468320 |
| 18 | 599074560 |
| 19 | 876634920 |
| 20 | 1257711840 |
| 21 | 1772629320 |
| 22 | 2458431360 |
| 23 | 3359941200 |
| 24 | 4530926400 |
[0,0,840,10080,57960,228480,710640,1874880, 4379760,9313920,18378360,34114080,60180120, 101687040,165590880,261152640,400468320,599074560, 876634920,1257711840,1772629320,2458431360, 3359941200,4530926400] |