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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 4 |
| 4 | 90 |
| 5 | 2448 |
| 6 | 79716 |
| 7 | 3058740 |
| 8 | 135637242 |
| 9 | 6835557984 |
| 10 | 386119895256 |
| 11 | 24170805494868 |
| 12 | 1661105052140226 |
| 13 | 124342746871407984 |
| 14 | 10070793262851698412 |
| 15 | 877493877654988612836 |
| 16 | 81848857574562663295026 |
| 17 | 8137513480199793111630528 |
| 18 | 859067817713438540813133744 |
| 19 | 95973644392465888508242272804 |
| 20 | 11312379843382901418721437545706 |
[1,0,0,4,90,2448,79716,3058740,135637242, 6835557984,386119895256,24170805494868, 1661105052140226,124342746871407984, 10070793262851698412,877493877654988612836, 81848857574562663295026,8137513480199793111630528, 859067817713438540813133744, 95973644392465888508242272804, 11312379843382901418721437545706] |