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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 3 |
| 4 | 152 |
| 5 | 930 |
| 6 | 42804 |
| 7 | 574140 |
| 8 | 27267456 |
| 9 | 613793376 |
| 10 | 31378237200 |
| 11 | 1021391030880 |
| 12 | 57256014687552 |
| 13 | 2456525677525920 |
| 14 | 152135168050833408 |
| 15 | 8093376365276966400 |
| 16 | 554533365688970342400 |
| 17 | 35081649646969248529920 |
| 18 | 2653840371674014197608448 |
[1,0,2,3,152,930,42804,574140,27267456,613793376, 31378237200,1021391030880,57256014687552, 2456525677525920,152135168050833408, 8093376365276966400,554533365688970342400, 35081649646969248529920,2653840371674014197608448] |