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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 10 |
| 4 | 28 |
| 5 | 84 |
| 6 | 282 |
| 7 | 968 |
| 8 | 3574 |
| 9 | 13526 |
| 10 | 53248 |
| 11 | 215288 |
| 12 | 889072 |
| 13 | 3749808 |
| 14 | 16120368 |
| 15 | 70569136 |
| 16 | 314384296 |
| 17 | 1424490556 |
| 18 | 6561255338 |
| 19 | 30706715780 |
| 20 | 145947430208 |
| 21 | 704170163362 |
| 22 | 3447329246534 |
| 23 | 17116783509170 |
| 24 | 86161074446406 |
| 25 | 439511863198824 |
| 26 | 2271055875812692 |
[1,2,4,10,28,84,282,968,3574,13526,53248,215288, 889072,3749808,16120368,70569136,314384296, 1424490556,6561255338,30706715780,145947430208, 704170163362,3447329246534,17116783509170, 86161074446406,439511863198824,2271055875812692] |