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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 42 |
| 5 | 4094 |
| 6 | 98210640 |
| 7 | 148947659711650464 |
| 8 | 872404773126414633407736134582136832 |
| 9 | 88627167739308536281147085615274891669779458770791192509009429292662497280 |
[1,2,6,42,4094,98210640,148947659711650464, 872404773126414633407736134582136832, 88627167739308536281147085615274891669779458770791\ 192509009429292662497280] |