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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 32 |
| 3 | 248 |
| 4 | 1933 |
| 5 | 15070 |
| 6 | 117494 |
| 7 | 916061 |
| 8 | 7142233 |
| 9 | 55685704 |
| 10 | 434163629 |
| 11 | 3385035032 |
| 12 | 26392036123 |
| 13 | 205770269515 |
| 14 | 1604325017633 |
| 15 | 12508409345459 |
| 16 | 97524069396190 |
| 17 | 760363995846334 |
| 18 | 5928315027859268 |
| 19 | 46221177306565661 |
| 20 | 360371745017815198 |
[4,32,248,1933,15070,117494,916061,7142233, 55685704,434163629,3385035032,26392036123, 205770269515,1604325017633,12508409345459, 97524069396190,760363995846334,5928315027859268, 46221177306565661,360371745017815198] |