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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 14 |
| 4 | 64 |
| 5 | 322 |
| 6 | 2054 |
| 7 | 14380 |
| 8 | 116722 |
| 9 | 1060580 |
| 10 | 10636042 |
| 11 | 116996464 |
| 12 | 1411275650 |
| 13 | 18346583452 |
| 14 | 256869465610 |
| 15 | 3856674412952 |
| 16 | 61743633813634 |
| 17 | 1049641774831780 |
| 18 | 18896533652098442 |
| 19 | 359034139389870400 |
| 20 | 7182372973523436802 |
| 21 | 150833211474559084844 |
[1,4,14,64,322,2054,14380,116722,1060580,10636042, 116996464,1411275650,18346583452,256869465610, 3856674412952,61743633813634,1049641774831780, 18896533652098442,359034139389870400, 7182372973523436802,150833211474559084844] |