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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 8 |
| 3 | 87 |
| 4 | 1428 |
| 5 | 31125 |
| 6 | 847818 |
| 7 | 27785205 |
| 8 | 1065267864 |
| 9 | 46802921769 |
| 10 | 2319200977230 |
| 11 | 127985909702409 |
| 12 | 7785440359004916 |
| 13 | 517616528753919933 |
| 14 | 37344834374921549154 |
| 15 | 2906043724955696034285 |
| 16 | 242627026212699695954352 |
| 17 | 21634774261037677172406609 |
| 18 | 2052077586846349144929739542 |
[1,1,8,87,1428,31125,847818,27785205,1065267864, 46802921769,2319200977230,127985909702409, 7785440359004916,517616528753919933, 37344834374921549154,2906043724955696034285, 242627026212699695954352, 21634774261037677172406609, 2052077586846349144929739542] |