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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 25 |
| 3 | 249 |
| 4 | 2010 |
| 5 | 15892 |
| 6 | 124104 |
| 7 | 966863 |
| 8 | 7523192 |
| 9 | 58488468 |
| 10 | 454572611 |
| 11 | 3532430740 |
| 12 | 27448191693 |
| 13 | 213274779277 |
| 14 | 1657138893969 |
| 15 | 12875834577268 |
| 16 | 100043881281917 |
| 17 | 777329345240298 |
| 18 | 6039754896804956 |
| 19 | 46928150488134892 |
| 20 | 364625891287391839 |
[4,25,249,2010,15892,124104,966863,7523192, 58488468,454572611,3532430740,27448191693, 213274779277,1657138893969,12875834577268, 100043881281917,777329345240298,6039754896804956, 46928150488134892,364625891287391839] |