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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 24 |
| 4 | 132 |
| 5 | 500 |
| 6 | 2728 |
| 7 | 10324 |
| 8 | 56651 |
| 9 | 215323 |
| 10 | 1191987 |
| 11 | 4549786 |
| 12 | 25420734 |
| 13 | 97369588 |
| 14 | 548884043 |
| 15 | 2108335364 |
| 16 | 11983465575 |
| 17 | 46136052623 |
| 18 | 264215445322 |
| 19 | 1019173758683 |
| 20 | 5876647410170 |
| 21 | 22705355331214 |
| 22 | 131727633042981 |
| 23 | 509673506069905 |
| 24 | 2973264727753047 |
| 25 | 11518483809430525 |
[1,6,24,132,500,2728,10324,56651,215323,1191987, 4549786,25420734,97369588,548884043,2108335364, 11983465575,46136052623,264215445322, 1019173758683,5876647410170,22705355331214, 131727633042981,509673506069905,2973264727753047, 11518483809430525] |