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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 12 |
| 3 | 41 |
| 4 | 159 |
| 5 | 685 |
| 6 | 3233 |
| 7 | 16533 |
| 8 | 90817 |
| 9 | 531812 |
| 10 | 3295779 |
| 11 | 21456363 |
| 12 | 145645809 |
| 13 | 1023308083 |
| 14 | 7391587656 |
| 15 | 54563960012 |
| 16 | 409583330514 |
| 17 | 3113836080693 |
| 18 | 23899707589707 |
| 19 | 184747234605277 |
| 20 | 1435668152296255 |
| 21 | 11200152289621048 |
[4,12,41,159,685,3233,16533,90817,531812,3295779, 21456363,145645809,1023308083,7391587656, 54563960012,409583330514,3113836080693, 23899707589707,184747234605277,1435668152296255, 11200152289621048] |