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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 43 |
| 5 | 152 |
| 6 | 575 |
| 7 | 2314 |
| 8 | 9870 |
| 9 | 44535 |
| 10 | 212242 |
| 11 | 1066327 |
| 12 | 5635369 |
| 13 | 31254046 |
| 14 | 181478525 |
| 15 | 1100796500 |
| 16 | 6960517564 |
| 17 | 45791562573 |
| 18 | 312867812160 |
| 19 | 2216414659873 |
| 20 | 16255306015303 |
| 21 | 123249020783620 |
| 22 | 964832925700315 |
| 23 | 7788943826367902 |
| 24 | 64770559745065226 |
| 25 | 554239921143411715 |
[1,4,13,43,152,575,2314,9870,44535,212242,1066327, 5635369,31254046,181478525,1100796500,6960517564, 45791562573,312867812160,2216414659873, 16255306015303,123249020783620,964832925700315, 7788943826367902,64770559745065226, 554239921143411715] |