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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 25 |
| 5 | 113 |
| 6 | 548 |
| 7 | 2770 |
| 8 | 14426 |
| 9 | 76851 |
| 10 | 416848 |
| 11 | 2294224 |
| 12 | 12780394 |
| 13 | 71924647 |
| 14 | 408310668 |
| 15 | 2335443077 |
| 16 | 13446130438 |
| 17 | 77863375126 |
| 18 | 453203435319 |
| 19 | 2649957419351 |
| 20 | 15558520126830 |
| 21 | 91687179000949 |
| 22 | 542139459641933 |
| 23 | 3215484006733932 |
| 24 | 19125017153077911 |
[0,1,2,6,25,113,548,2770,14426,76851,416848, 2294224,12780394,71924647,408310668,2335443077, 13446130438,77863375126,453203435319, 2649957419351,15558520126830,91687179000949, 542139459641933,3215484006733932, 19125017153077911] |