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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 31 |
| 4 | 144 |
| 5 | 637 |
| 6 | 2730 |
| 7 | 11467 |
| 8 | 47508 |
| 9 | 194953 |
| 10 | 794574 |
| 11 | 3222583 |
| 12 | 13023192 |
| 13 | 52491349 |
| 14 | 211161138 |
| 15 | 848231779 |
| 16 | 3403688796 |
| 17 | 13647040225 |
| 18 | 54685016022 |
| 19 | 219030629455 |
| 20 | 876994213920 |
| 21 | 3510591943981 |
| 22 | 14050213040826 |
| 23 | 56224387958011 |
[0,1,6,31,144,637,2730,11467,47508,194953,794574, 3222583,13023192,52491349,211161138,848231779, 3403688796,13647040225,54685016022,219030629455, 876994213920,3510591943981,14050213040826, 56224387958011] |