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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 26 |
| 3 | 166 |
| 4 | 1132 |
| 5 | 7467 |
| 6 | 49463 |
| 7 | 327682 |
| 8 | 2171860 |
| 9 | 14390221 |
| 10 | 95353162 |
| 11 | 631825762 |
| 12 | 4186583834 |
| 13 | 27740954262 |
| 14 | 183815964468 |
| 15 | 1217993552767 |
| 16 | 8070617253871 |
| 17 | 53477180775990 |
| 18 | 354348220790578 |
| 19 | 2347967100599964 |
| 20 | 15557999665702100 |
[4,26,166,1132,7467,49463,327682,2171860,14390221, 95353162,631825762,4186583834,27740954262, 183815964468,1217993552767,8070617253871, 53477180775990,354348220790578,2347967100599964, 15557999665702100] |