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| n | a(n) |
|---|---|
| 1 | 648 |
| 2 | 4050 |
| 3 | 27378 |
| 4 | 175232 |
| 5 | 1131008 |
| 6 | 7311488 |
| 7 | 47258642 |
| 8 | 305390898 |
| 9 | 1973176200 |
| 10 | 12751406208 |
| 11 | 82400136968 |
| 12 | 532464529058 |
| 13 | 3440804225762 |
| 14 | 22234526147072 |
| 15 | 143679727411200 |
| 16 | 928460232000000 |
| 17 | 5999721595740450 |
| 18 | 38770275955862882 |
[648,4050,27378,175232,1131008,7311488,47258642, 305390898,1973176200,12751406208,82400136968, 532464529058,3440804225762,22234526147072, 143679727411200,928460232000000,5999721595740450, 38770275955862882] |