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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 8 |
| 3 | 31 |
| 4 | 144 |
| 5 | 628 |
| 6 | 3040 |
| 7 | 13980 |
| 8 | 68716 |
| 9 | 324720 |
| 10 | 1607746 |
| 11 | 7718620 |
| 12 | 38364784 |
| 13 | 186045893 |
| 14 | 926767620 |
| 15 | 4524889398 |
| 16 | 22569907648 |
| 17 | 110727110550 |
| 18 | 552750968483 |
| 19 | 2721350588337 |
| 20 | 13592076219724 |
| 21 | 67096009253821 |
| 22 | 335232053210020 |
| 23 | 1658251490729481 |
| 24 | 8287003862834721 |
| 25 | 41058944515130466 |
| 26 | 205220845700504006 |
[1,2,8,31,144,628,3040,13980,68716,324720,1607746, 7718620,38364784,186045893,926767620,4524889398, 22569907648,110727110550,552750968483, 2721350588337,13592076219724,67096009253821, 335232053210020,1658251490729481,8287003862834721, 41058944515130466,205220845700504006] |