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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 28 |
| 3 | 476 |
| 4 | 1386 |
| 5 | 8106 |
| 6 | 117936 |
| 7 | 322764 |
| 8 | 1440579 |
| 9 | 6172495 |
| 10 | 99773646 |
| 11 | 232110704 |
| 12 | 981073576 |
| 13 | 3329628176 |
| 14 | 14040114012 |
| 15 | 224848217580 |
| 16 | 490210909629 |
| 17 | 1828885568055 |
| 18 | 5750093241172 |
| 19 | 20040621544916 |
| 20 | 69910543160794 |
| 21 | 1238596672832718 |
| 22 | 2451410591056280 |
| 23 | 8705347941656016 |
[1,7,28,476,1386,8106,117936,322764,1440579, 6172495,99773646,232110704,981073576,3329628176, 14040114012,224848217580,490210909629, 1828885568055,5750093241172,20040621544916, 69910543160794,1238596672832718,2451410591056280, 8705347941656016] |