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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 44 |
| 5 | 144 |
| 6 | 478 |
| 7 | 1573 |
| 8 | 5193 |
| 9 | 17118 |
| 10 | 56457 |
| 11 | 186153 |
| 12 | 613865 |
| 13 | 2024192 |
| 14 | 6674843 |
| 15 | 22010313 |
| 16 | 72579382 |
| 17 | 239331323 |
| 18 | 789198395 |
| 19 | 2602391853 |
| 20 | 8581422014 |
| 21 | 28297352194 |
| 22 | 93310894654 |
| 23 | 307693910316 |
| 24 | 1014624748161 |
| 25 | 3345738548716 |
| 26 | 11032617200372 |
| 27 | 36380201398917 |
[1,1,4,13,44,144,478,1573,5193,17118,56457,186153, 613865,2024192,6674843,22010313,72579382, 239331323,789198395,2602391853,8581422014, 28297352194,93310894654,307693910316, 1014624748161,3345738548716,11032617200372, 36380201398917] |