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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 60 |
| 3 | 1204 |
| 4 | 27724 |
| 5 | 691812 |
| 6 | 18198492 |
| 7 | 496924692 |
| 8 | 13951437804 |
| 9 | 400212569284 |
| 10 | 11679079547260 |
| 11 | 345621250279284 |
| 12 | 10347645099250060 |
| 13 | 312857431914558244 |
| 14 | 9538937406065229084 |
| 15 | 292961855077076241108 |
| 16 | 9054857076142602126636 |
| 17 | 281439018537947499788676 |
| 18 | 8791174819979940884130492 |
[1,4,60,1204,27724,691812,18198492,496924692, 13951437804,400212569284,11679079547260, 345621250279284,10347645099250060, 312857431914558244,9538937406065229084, 292961855077076241108,9054857076142602126636, 281439018537947499788676, 8791174819979940884130492] |