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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 56 |
| 5 | 226 |
| 6 | 993 |
| 7 | 4387 |
| 8 | 19921 |
| 9 | 91299 |
| 10 | 424146 |
| 11 | 1984585 |
| 12 | 9359316 |
| 13 | 44377511 |
| 14 | 211482643 |
| 15 | 1011882904 |
| 16 | 4858879581 |
| 17 | 23401436915 |
| 18 | 113006754137 |
| 19 | 546971963058 |
| 20 | 2652858824592 |
| 21 | 12889882826150 |
| 22 | 62731663049380 |
| 23 | 305741726340137 |
| 24 | 1492077885605746 |
| 25 | 7290260353306069 |
| 26 | 35658493834967239 |
| 27 | 174586407858085867 |
[1,1,4,13,56,226,993,4387,19921,91299,424146, 1984585,9359316,44377511,211482643,1011882904, 4858879581,23401436915,113006754137,546971963058, 2652858824592,12889882826150,62731663049380, 305741726340137,1492077885605746,7290260353306069, 35658493834967239,174586407858085867] |