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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 42 |
| 3 | 612 |
| 4 | 10387 |
| 5 | 192312 |
| 6 | 3766316 |
| 7 | 76716624 |
| 8 | 1608691229 |
| 9 | 34495221722 |
| 10 | 752911467734 |
| 11 | 16671973428486 |
| 12 | 373609441084507 |
| 13 | 8457057155407906 |
| 14 | 193087102810266948 |
| 15 | 4441320670474030222 |
| 16 | 102821800799622552713 |
| 17 | 2394063264658388861914 |
| 18 | 56025225620739219372819 |
[1,4,42,612,10387,192312,3766316,76716624, 1608691229,34495221722,752911467734, 16671973428486,373609441084507,8457057155407906, 193087102810266948,4441320670474030222, 102821800799622552713,2394063264658388861914, 56025225620739219372819] |