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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 17 |
| 4 | 73 |
| 5 | 314 |
| 6 | 1351 |
| 7 | 5813 |
| 8 | 25012 |
| 9 | 107621 |
| 10 | 463069 |
| 11 | 1992482 |
| 12 | 8573203 |
| 13 | 36888569 |
| 14 | 158723236 |
| 15 | 682950473 |
| 16 | 2938582657 |
| 17 | 12644061866 |
| 18 | 54404561359 |
| 19 | 234090621197 |
| 20 | 1007239421908 |
| 21 | 4333925245949 |
| 22 | 18647907964021 |
| 23 | 80237764082258 |
[0,1,4,17,73,314,1351,5813,25012,107621,463069, 1992482,8573203,36888569,158723236,682950473, 2938582657,12644061866,54404561359,234090621197, 1007239421908,4333925245949,18647907964021, 80237764082258] |