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| n | a(n) |
|---|---|
| 0 | 15 |
| 1 | 45 |
| 2 | 630 |
| 3 | 25200 |
| 4 | 32004000 |
| 5 | 508031496000 |
| 6 | 128015872500032496000 |
| 7 | 3670698694547655407496988066168944000 |
| 8 | 10302657959650317880463349610273001290502485245258650172717840000 |
[15,45,630,25200,32004000,508031496000, 128015872500032496000, 3670698694547655407496988066168944000, 10302657959650317880463349610273001290502485245258\ 650172717840000] |