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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 17 |
| 4 | 50 |
| 5 | 147 |
| 6 | 435 |
| 7 | 1290 |
| 8 | 3834 |
| 9 | 11411 |
| 10 | 34001 |
| 11 | 101400 |
| 12 | 302615 |
| 13 | 903632 |
| 14 | 2699598 |
| 15 | 8068257 |
| 16 | 24121674 |
| 17 | 72137547 |
| 18 | 215786649 |
| 19 | 645629160 |
| 20 | 1932081885 |
| 21 | 5782851966 |
| 22 | 17311097568 |
| 23 | 51828203475 |
| 24 | 155188936431 |
| 25 | 464732722872 |
[1,2,6,17,50,147,435,1290,3834,11411,34001,101400, 302615,903632,2699598,8068257,24121674,72137547, 215786649,645629160,1932081885,5782851966, 17311097568,51828203475,155188936431,464732722872] |