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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 21 |
| 4 | 80 |
| 5 | 322 |
| 6 | 1347 |
| 7 | 5796 |
| 8 | 25477 |
| 9 | 113874 |
| 10 | 515818 |
| 11 | 2362069 |
| 12 | 10914502 |
| 13 | 50815843 |
| 14 | 238113099 |
| 15 | 1121913889 |
| 16 | 5311353117 |
| 17 | 25249666932 |
| 18 | 120473327642 |
| 19 | 576668900224 |
| 20 | 2768258625991 |
| 21 | 13322888865844 |
| 22 | 64266963824287 |
| 23 | 310653575562268 |
| 24 | 1504452962143164 |
| 25 | 7298269464489332 |
| 26 | 35459668011919995 |
| 27 | 172530211194057549 |
[1,2,6,21,80,322,1347,5796,25477,113874,515818, 2362069,10914502,50815843,238113099,1121913889, 5311353117,25249666932,120473327642,576668900224, 2768258625991,13322888865844,64266963824287, 310653575562268,1504452962143164,7298269464489332, 35459668011919995,172530211194057549] |