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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 6 |
| 4 | 28 |
| 5 | 121 |
| 6 | 508 |
| 7 | 2109 |
| 8 | 8723 |
| 9 | 36065 |
| 10 | 149277 |
| 11 | 618961 |
| 12 | 2571503 |
| 13 | 10704390 |
| 14 | 44641793 |
| 15 | 186492242 |
| 16 | 780275596 |
| 17 | 3269135406 |
| 18 | 13713525610 |
| 19 | 57588530626 |
| 20 | 242068874444 |
| 21 | 1018378855512 |
| 22 | 4287501276956 |
| 23 | 18062827159136 |
| 24 | 76141329903018 |
[1,6,28,121,508,2109,8723,36065,149277,618961, 2571503,10704390,44641793,186492242,780275596, 3269135406,13713525610,57588530626,242068874444, 1018378855512,4287501276956,18062827159136, 76141329903018] |