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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 31 |
| 4 | 300 |
| 5 | 3251 |
| 6 | 37744 |
| 7 | 459060 |
| 8 | 5773548 |
| 9 | 74474455 |
| 10 | 979872036 |
| 11 | 13099102575 |
| 12 | 177414673488 |
| 13 | 2429310288468 |
| 14 | 33574008073120 |
| 15 | 467717206216760 |
| 16 | 6560977611629676 |
| 17 | 92595131510426943 |
| 18 | 1313820730347196300 |
| 19 | 18730821529411507725 |
| 20 | 268185082351558093260 |
[1,4,31,300,3251,37744,459060,5773548,74474455, 979872036,13099102575,177414673488,2429310288468, 33574008073120,467717206216760,6560977611629676, 92595131510426943,1313820730347196300, 18730821529411507725,268185082351558093260] |