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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 6 |
| 3 | 18 |
| 4 | 56 |
| 5 | 188 |
| 6 | 695 |
| 7 | 2838 |
| 8 | 12726 |
| 9 | 62140 |
| 10 | 327760 |
| 11 | 1854488 |
| 12 | 11189273 |
| 13 | 71627546 |
| 14 | 484332314 |
| 15 | 3446042310 |
| 16 | 25712613664 |
| 17 | 200599911596 |
| 18 | 1632055365951 |
| 19 | 13814906940846 |
| 20 | 121414108567114 |
| 21 | 1105838412755384 |
| 22 | 10420517690466168 |
| 23 | 101439025287805552 |
| 24 | 1018689421191417393 |
[2,6,18,56,188,695,2838,12726,62140,327760, 1854488,11189273,71627546,484332314,3446042310, 25712613664,200599911596,1632055365951, 13814906940846,121414108567114,1105838412755384, 10420517690466168,101439025287805552, 1018689421191417393] |