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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 8 |
| 4 | 20 |
| 5 | 50 |
| 6 | 126 |
| 7 | 322 |
| 8 | 834 |
| 9 | 2187 |
| 10 | 5797 |
| 11 | 15510 |
| 12 | 41834 |
| 13 | 113633 |
| 14 | 310571 |
| 15 | 853466 |
| 16 | 2356778 |
| 17 | 6536381 |
| 18 | 18199283 |
| 19 | 50852018 |
| 20 | 142547558 |
| 21 | 400763222 |
| 22 | 1129760414 |
| 23 | 3192727796 |
| 24 | 9043402500 |
| 25 | 25669818475 |
| 26 | 73007772801 |
| 27 | 208023278208 |
[1,3,8,20,50,126,322,834,2187,5797,15510,41834, 113633,310571,853466,2356778,6536381,18199283, 50852018,142547558,400763222,1129760414, 3192727796,9043402500,25669818475,73007772801, 208023278208] |