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| n | a(n) |
|---|---|
| 1 | 18 |
| 2 | 324 |
| 3 | 1278 |
| 4 | 5041 |
| 5 | 39831 |
| 6 | 314721 |
| 7 | 1726758 |
| 8 | 9474084 |
| 9 | 62431074 |
| 10 | 411400089 |
| 11 | 2464567047 |
| 12 | 14764437081 |
| 13 | 92881236582 |
| 14 | 584304302404 |
| 15 | 3583711091042 |
| 16 | 21979959981841 |
| 17 | 136591044276099 |
| 18 | 848823810045561 |
| 19 | 5238992009252400 |
[18,324,1278,5041,39831,314721,1726758,9474084, 62431074,411400089,2464567047,14764437081, 92881236582,584304302404,3583711091042, 21979959981841,136591044276099,848823810045561, 5238992009252400] |