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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 6 |
| 3 | 72 |
| 4 | 910 |
| 5 | 12000 |
| 6 | 163086 |
| 7 | 2266544 |
| 8 | 32043726 |
| 9 | 459167040 |
| 10 | 6651400756 |
| 11 | 97214919648 |
| 12 | 1431514320886 |
| 13 | 21213380196736 |
| 14 | 316072831033350 |
| 15 | 4731683468079072 |
| 16 | 71128104013487310 |
| 17 | 1073134004384407680 |
| 18 | 16243463355081280080 |
| 19 | 246585461357885877920 |
[1,0,6,72,910,12000,163086,2266544,32043726, 459167040,6651400756,97214919648,1431514320886, 21213380196736,316072831033350,4731683468079072, 71128104013487310,1073134004384407680, 16243463355081280080,246585461357885877920] |