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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 58 |
| 5 | 223 |
| 6 | 1035 |
| 7 | 4385 |
| 8 | 20837 |
| 9 | 92832 |
| 10 | 447686 |
| 11 | 2056408 |
| 12 | 10011840 |
| 13 | 46924966 |
| 14 | 229928748 |
| 15 | 1092889534 |
| 16 | 5379243634 |
| 17 | 25829380711 |
| 18 | 127549443682 |
| 19 | 617106718099 |
| 20 | 3054805216270 |
| 21 | 14865442568292 |
| 22 | 73723871989651 |
| 23 | 360379717873853 |
| 24 | 1789852017157827 |
| 25 | 8780525377135672 |
| 26 | 43658728589830775 |
| 27 | 214793394110780838 |
[1,1,4,13,58,223,1035,4385,20837,92832,447686, 2056408,10011840,46924966,229928748,1092889534, 5379243634,25829380711,127549443682,617106718099, 3054805216270,14865442568292,73723871989651, 360379717873853,1789852017157827,8780525377135672, 43658728589830775,214793394110780838] |