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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 16 |
| 5 | 120 |
| 6 | 640 |
| 7 | 2800 |
| 8 | 10752 |
| 9 | 37632 |
| 10 | 122880 |
| 11 | 380160 |
| 12 | 1126400 |
| 13 | 3221504 |
| 14 | 8945664 |
| 15 | 24227840 |
| 16 | 64225280 |
| 17 | 167116800 |
| 18 | 427819008 |
| 19 | 1079574528 |
| 20 | 2689597440 |
| 21 | 6624378880 |
| 22 | 16148070400 |
| 23 | 38997590016 |
| 24 | 93381984256 |
| 25 | 221878681600 |
| 26 | 523449139200 |
| 27 | 1226833920000 |
| 28 | 2858032300032 |
[0,0,1,16,120,640,2800,10752,37632,122880,380160, 1126400,3221504,8945664,24227840,64225280, 167116800,427819008,1079574528,2689597440, 6624378880,16148070400,38997590016,93381984256, 221878681600,523449139200,1226833920000, 2858032300032] |