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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 2 |
| 3 | 14 |
| 4 | 18 |
| 5 | 62 |
| 6 | 566 |
| 7 | 1094 |
| 8 | 3954 |
| 9 | 17150 |
| 10 | 646182 |
| 11 | 1460054 |
| 12 | 7152294 |
| 13 | 32145622 |
| 14 | 215489878 |
| 15 | 15152657534 |
| 16 | 41699885554 |
| 17 | 237383066942 |
| 18 | 1205858271302 |
| 19 | 7890800135702 |
| 20 | 63929081762358 |
| 21 | 8131982041916390 |
| 22 | 26062267807810918 |
[1,2,2,14,18,62,566,1094,3954,17150,646182, 1460054,7152294,32145622,215489878,15152657534, 41699885554,237383066942,1205858271302, 7890800135702,63929081762358,8131982041916390, 26062267807810918] |