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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 19 |
| 4 | 66 |
| 5 | 243 |
| 6 | 930 |
| 7 | 3677 |
| 8 | 14911 |
| 9 | 61634 |
| 10 | 259234 |
| 11 | 1105147 |
| 12 | 4767937 |
| 13 | 20782106 |
| 14 | 91385250 |
| 15 | 405000507 |
| 16 | 1807317447 |
| 17 | 8114777154 |
| 18 | 36636893847 |
| 19 | 166234252180 |
| 20 | 757672572779 |
| 21 | 3467591514145 |
| 22 | 15929670995318 |
| 23 | 73431924702453 |
| 24 | 339581832393760 |
| 25 | 1575001867846787 |
| 26 | 7324903642155787 |
| 27 | 34152593363634683 |
[1,2,6,19,66,243,930,3677,14911,61634,259234, 1105147,4767937,20782106,91385250,405000507, 1807317447,8114777154,36636893847,166234252180, 757672572779,3467591514145,15929670995318, 73431924702453,339581832393760,1575001867846787, 7324903642155787,34152593363634683] |