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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 5 |
| 2 | 20 |
| 3 | 70 |
| 4 | 240 |
| 5 | 810 |
| 6 | 2730 |
| 7 | 9180 |
| 8 | 30870 |
| 9 | 103770 |
| 10 | 348840 |
| 11 | 1172610 |
| 12 | 3941730 |
| 13 | 13249980 |
| 14 | 44539470 |
| 15 | 149717970 |
| 16 | 503272440 |
| 17 | 1691734410 |
| 18 | 5686712730 |
| 19 | 19115706780 |
| 20 | 64256852070 |
| 21 | 215997400170 |
| 22 | 726068516040 |
| 23 | 2440656636210 |
| 24 | 8204191055730 |
| 25 | 27578131979580 |
| 26 | 92703029288670 |
[1,5,20,70,240,810,2730,9180,30870,103770,348840, 1172610,3941730,13249980,44539470,149717970, 503272440,1691734410,5686712730,19115706780, 64256852070,215997400170,726068516040, 2440656636210,8204191055730,27578131979580, 92703029288670] |