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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 10 |
| 4 | 30 |
| 5 | 104 |
| 6 | 406 |
| 7 | 1754 |
| 8 | 8280 |
| 9 | 42294 |
| 10 | 231950 |
| 11 | 1357140 |
| 12 | 8427194 |
| 13 | 55288874 |
| 14 | 381798644 |
| 15 | 2765917090 |
| 16 | 20960284294 |
| 17 | 165729739608 |
| 18 | 1364153612318 |
| 19 | 11665484410114 |
| 20 | 103448316470744 |
| 21 | 949739632313502 |
| 22 | 9013431476894646 |
| 23 | 88304011710168692 |
| 24 | 891917738589610578 |
| 25 | 9277180664459998706 |
[1,2,4,10,30,104,406,1754,8280,42294,231950, 1357140,8427194,55288874,381798644,2765917090, 20960284294,165729739608,1364153612318, 11665484410114,103448316470744,949739632313502, 9013431476894646,88304011710168692, 891917738589610578,9277180664459998706] |