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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 57 |
| 5 | 223 |
| 6 | 1028 |
| 7 | 4392 |
| 8 | 20801 |
| 9 | 93192 |
| 10 | 448388 |
| 11 | 2068395 |
| 12 | 10052266 |
| 13 | 47272935 |
| 14 | 231307163 |
| 15 | 1102408601 |
| 16 | 5419992341 |
| 17 | 26082078971 |
| 18 | 128680642305 |
| 19 | 623701125067 |
| 20 | 3085177756781 |
| 21 | 15035715248503 |
| 22 | 74523449457592 |
| 23 | 364745828732076 |
| 24 | 1810638694267339 |
| 25 | 8891946466493735 |
| 26 | 44194574931517811 |
| 27 | 217627063614150518 |
[1,1,4,13,57,223,1028,4392,20801,93192,448388, 2068395,10052266,47272935,231307163,1102408601, 5419992341,26082078971,128680642305,623701125067, 3085177756781,15035715248503,74523449457592, 364745828732076,1810638694267339,8891946466493735, 44194574931517811,217627063614150518] |