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| n | a(n) |
|---|---|
| 1 | 20 |
| 2 | 124 |
| 3 | 643 |
| 4 | 2934 |
| 5 | 11810 |
| 6 | 42295 |
| 7 | 136553 |
| 8 | 402898 |
| 9 | 1099681 |
| 10 | 2805516 |
| 11 | 6748051 |
| 12 | 15412421 |
| 13 | 33626114 |
| 14 | 70430760 |
| 15 | 142218700 |
| 16 | 277853319 |
| 17 | 526833214 |
| 18 | 972034792 |
| 19 | 1749218167 |
| 20 | 3076360168 |
| 21 | 5297051430 |
| 22 | 8943742393 |
| 23 | 14828643583 |
| 24 | 24172697248 |
[20,124,643,2934,11810,42295,136553,402898, 1099681,2805516,6748051,15412421,33626114, 70430760,142218700,277853319,526833214,972034792, 1749218167,3076360168,5297051430,8943742393, 14828643583,24172697248] |