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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 5 |
| 2 | 18 |
| 3 | 67 |
| 4 | 250 |
| 5 | 933 |
| 6 | 3482 |
| 7 | 12995 |
| 8 | 48498 |
| 9 | 180997 |
| 10 | 675490 |
| 11 | 2520963 |
| 12 | 9408362 |
| 13 | 35112485 |
| 14 | 131041578 |
| 15 | 489053827 |
| 16 | 1825173730 |
| 17 | 6811641093 |
| 18 | 25421390642 |
| 19 | 94873921475 |
| 20 | 354074295258 |
| 21 | 1321423259557 |
| 22 | 4931618742970 |
| 23 | 18405051712323 |
| 24 | 68688588106322 |
| 25 | 256349300712965 |
[2,5,18,67,250,933,3482,12995,48498,180997,675490, 2520963,9408362,35112485,131041578,489053827, 1825173730,6811641093,25421390642,94873921475, 354074295258,1321423259557,4931618742970, 18405051712323,68688588106322,256349300712965] |