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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 22 |
| 4 | 102 |
| 5 | 474 |
| 6 | 2250 |
| 7 | 10910 |
| 8 | 53886 |
| 9 | 270322 |
| 10 | 1373970 |
| 11 | 7061542 |
| 12 | 36639702 |
| 13 | 191677386 |
| 14 | 1009942362 |
| 15 | 5354887470 |
| 16 | 28550730222 |
| 17 | 152979375842 |
| 18 | 823329316386 |
| 19 | 4448856020534 |
| 20 | 24126427982406 |
| 21 | 131270003806906 |
| 22 | 716377546590186 |
| 23 | 3920251765198782 |
| 24 | 21507301494123102 |
| 25 | 118269635529457874 |
[1,2,4,22,102,474,2250,10910,53886,270322,1373970, 7061542,36639702,191677386,1009942362,5354887470, 28550730222,152979375842,823329316386, 4448856020534,24126427982406,131270003806906, 716377546590186,3920251765198782, 21507301494123102,118269635529457874] |