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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 72 |
| 3 | 978 |
| 4 | 14016 |
| 5 | 207006 |
| 6 | 3116952 |
| 7 | 47568618 |
| 8 | 733189632 |
| 9 | 11387193846 |
| 10 | 177923724072 |
| 11 | 2793666465090 |
| 12 | 44042615547456 |
| 13 | 696708049377294 |
| 14 | 11053262513080440 |
| 15 | 175800225426741978 |
| 16 | 2802193910116429824 |
| 17 | 44752001810800994022 |
| 18 | 715924864099841086728 |
[1,6,72,978,14016,207006,3116952,47568618, 733189632,11387193846,177923724072,2793666465090, 44042615547456,696708049377294,11053262513080440, 175800225426741978,2802193910116429824, 44752001810800994022,715924864099841086728] |