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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 54 |
| 5 | 184 |
| 6 | 868 |
| 7 | 3270 |
| 8 | 15789 |
| 9 | 62535 |
| 10 | 305725 |
| 11 | 1250467 |
| 12 | 6158414 |
| 13 | 25763798 |
| 14 | 127467985 |
| 15 | 542192997 |
| 16 | 2690596202 |
| 17 | 11591354117 |
| 18 | 57638344104 |
| 19 | 250831973091 |
| 20 | 1249036545289 |
| 21 | 5480410135621 |
| 22 | 27317663458062 |
| 23 | 120682044327008 |
| 24 | 601992919806603 |
| 25 | 2674803141963889 |
| 26 | 13349816992232726 |
| 27 | 59610044516852108 |
[1,1,4,12,54,184,868,3270,15789,62535,305725, 1250467,6158414,25763798,127467985,542192997, 2690596202,11591354117,57638344104,250831973091, 1249036545289,5480410135621,27317663458062, 120682044327008,601992919806603,2674803141963889, 13349816992232726,59610044516852108] |