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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 9 |
| 4 | 22 |
| 5 | 55 |
| 6 | 136 |
| 7 | 331 |
| 8 | 798 |
| 9 | 1919 |
| 10 | 4620 |
| 11 | 11143 |
| 12 | 26906 |
| 13 | 64987 |
| 14 | 156944 |
| 15 | 378939 |
| 16 | 914822 |
| 17 | 2208455 |
| 18 | 5331476 |
| 19 | 12871151 |
| 20 | 31073778 |
| 21 | 75019219 |
| 22 | 181113240 |
| 23 | 437246723 |
| 24 | 1055606686 |
| 25 | 2548458047 |
| 26 | 6152518684 |
| 27 | 14853491319 |
| 28 | 35859501322 |
| 29 | 86572502155 |
| 30 | 209004522016 |
[1,2,4,9,22,55,136,331,798,1919,4620,11143,26906, 64987,156944,378939,914822,2208455,5331476, 12871151,31073778,75019219,181113240,437246723, 1055606686,2548458047,6152518684,14853491319, 35859501322,86572502155,209004522016] |