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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 12 |
| 5 | 60 |
| 6 | 792 |
| 7 | 1404 |
| 8 | 10704 |
| 9 | 31200 |
| 10 | 204972 |
| 11 | 349956 |
| 12 | 3727128 |
| 13 | 5065804 |
| 14 | 41572908 |
| 15 | 127198968 |
| 16 | 517279416 |
| 17 | 1041517620 |
| 18 | 11195605728 |
| 19 | 15012935676 |
| 20 | 135825494568 |
| 21 | 363040468328 |
| 22 | 1746669815460 |
| 23 | 3181465294092 |
[0,0,0,12,60,792,1404,10704,31200,204972,349956, 3727128,5065804,41572908,127198968,517279416, 1041517620,11195605728,15012935676,135825494568, 363040468328,1746669815460,3181465294092] |