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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 30 |
| 3 | 406 |
| 4 | 6327 |
| 5 | 107019 |
| 6 | 1909908 |
| 7 | 35399520 |
| 8 | 674842149 |
| 9 | 13147742322 |
| 10 | 260626484118 |
| 11 | 5239783981320 |
| 12 | 106585537781775 |
| 13 | 2189670831627678 |
| 14 | 45366284782209600 |
| 15 | 946815917066740800 |
| 16 | 19887218367823853937 |
| 17 | 420076689292591271325 |
| 18 | 8917736795123409615060 |
| 19 | 190161017612160607167948 |
| 20 | 4071301730663135449185705 |
[1,3,30,406,6327,107019,1909908,35399520, 674842149,13147742322,260626484118,5239783981320, 106585537781775,2189670831627678, 45366284782209600,946815917066740800, 19887218367823853937,420076689292591271325, 8917736795123409615060,190161017612160607167948, 4071301730663135449185705] |