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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 108 |
| 3 | 1620 |
| 4 | 20412 |
| 5 | 236196 |
| 6 | 2598156 |
| 7 | 27634932 |
| 8 | 286978140 |
| 9 | 2927177028 |
| 10 | 29443957164 |
| 11 | 292889889684 |
| 12 | 2887057484028 |
| 13 | 28242953648100 |
| 14 | 274521509459532 |
| 15 | 2653707924775476 |
| 16 | 25530500379736476 |
| 17 | 244598664928443012 |
[4,108,1620,20412,236196,2598156,27634932, 286978140,2927177028,29443957164,292889889684, 2887057484028,28242953648100,274521509459532, 2653707924775476,25530500379736476, 244598664928443012] |