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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 25 |
| 5 | 191 |
| 6 | 1981 |
| 7 | 24515 |
| 8 | 357393 |
| 9 | 6014944 |
| 10 | 114374701 |
| 11 | 2429126965 |
| 12 | 56973837097 |
| 13 | 1462548099325 |
| 14 | 40790689845725 |
| 15 | 1228180553509096 |
| 16 | 39706476998683809 |
| 17 | 1371869867621426343 |
| 18 | 50445615936195883981 |
| 19 | 1967026296214873286071 |
| 20 | 81070802180747506986681 |
[1,1,4,25,191,1981,24515,357393,6014944,114374701, 2429126965,56973837097,1462548099325, 40790689845725,1228180553509096,39706476998683809, 1371869867621426343,50445615936195883981, 1967026296214873286071,81070802180747506986681] |