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| n | a(n) |
|---|---|
| 0 | 4 |
| 1 | 27 |
| 2 | 192 |
| 3 | 1413 |
| 4 | 10620 |
| 5 | 80811 |
| 6 | 619272 |
| 7 | 4764501 |
| 8 | 36738036 |
| 9 | 283627899 |
| 10 | 2191179600 |
| 11 | 16934434533 |
| 12 | 130904287596 |
| 13 | 1012015111563 |
| 14 | 7824339848088 |
| 15 | 60495579495477 |
| 16 | 467743738958820 |
| 17 | 3616570744155099 |
| 18 | 27963305544220128 |
| 19 | 216212831973523269 |
[4,27,192,1413,10620,80811,619272,4764501, 36738036,283627899,2191179600,16934434533, 130904287596,1012015111563,7824339848088, 60495579495477,467743738958820,3616570744155099, 27963305544220128,216212831973523269] |