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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 38 |
| 5 | 140 |
| 6 | 524 |
| 7 | 1945 |
| 8 | 7607 |
| 9 | 30451 |
| 10 | 121729 |
| 11 | 495258 |
| 12 | 2052186 |
| 13 | 8535846 |
| 14 | 35743505 |
| 15 | 151371003 |
| 16 | 644849874 |
| 17 | 2757517776 |
| 18 | 11867704367 |
| 19 | 51360479505 |
| 20 | 223020860987 |
| 21 | 972134840405 |
| 22 | 4255707686907 |
| 23 | 18690007639491 |
| 24 | 82306784548572 |
| 25 | 363581658945791 |
| 26 | 1610644675412670 |
| 27 | 7151507718739511 |
[1,1,4,12,38,140,524,1945,7607,30451,121729, 495258,2052186,8535846,35743505,151371003, 644849874,2757517776,11867704367,51360479505, 223020860987,972134840405,4255707686907, 18690007639491,82306784548572,363581658945791, 1610644675412670,7151507718739511] |