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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 9 |
| 3 | 46 |
| 4 | 262 |
| 5 | 1590 |
| 6 | 10081 |
| 7 | 65986 |
| 8 | 442518 |
| 9 | 3024772 |
| 10 | 20996141 |
| 11 | 147603198 |
| 12 | 1048747751 |
| 13 | 7519252606 |
| 14 | 54332565330 |
| 15 | 395264527626 |
| 16 | 2892666314150 |
| 17 | 21281120904168 |
| 18 | 157299607827727 |
| 19 | 1167582500757800 |
| 20 | 8699515577902203 |
[1,2,9,46,262,1590,10081,65986,442518,3024772, 20996141,147603198,1048747751,7519252606, 54332565330,395264527626,2892666314150, 21281120904168,157299607827727,1167582500757800, 8699515577902203] |