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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 5 |
| 3 | 18 |
| 4 | 67 |
| 5 | 258 |
| 6 | 1054 |
| 7 | 4336 |
| 8 | 18390 |
| 9 | 79546 |
| 10 | 346789 |
| 11 | 1536833 |
| 12 | 6851192 |
| 13 | 30817749 |
| 14 | 139841923 |
| 15 | 637266870 |
| 16 | 2924137611 |
| 17 | 13471986079 |
| 18 | 62332135243 |
| 19 | 289725945703 |
| 20 | 1350473477529 |
| 21 | 6318046817743 |
| 22 | 29638426526944 |
| 23 | 139393817258063 |
| 24 | 657399735735674 |
| 25 | 3106530600891371 |
| 26 | 14713492006420404 |
| 27 | 69818773620573288 |
[1,2,5,18,67,258,1054,4336,18390,79546,346789, 1536833,6851192,30817749,139841923,637266870, 2924137611,13471986079,62332135243,289725945703, 1350473477529,6318046817743,29638426526944, 139393817258063,657399735735674,3106530600891371, 14713492006420404,69818773620573288] |