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| n | a(n) |
|---|---|
| 1 | 21 |
| 2 | 87 |
| 3 | 410 |
| 4 | 2645 |
| 5 | 14536 |
| 6 | 74998 |
| 7 | 371384 |
| 8 | 1780796 |
| 9 | 8327951 |
| 10 | 37770000 |
| 11 | 165587776 |
| 12 | 701557921 |
| 13 | 2877746302 |
| 14 | 11458190975 |
| 15 | 44395384830 |
| 16 | 167697083241 |
| 17 | 618401792448 |
| 18 | 2228478398270 |
| 19 | 7854147511367 |
[21,87,410,2645,14536,74998,371384,1780796, 8327951,37770000,165587776,701557921,2877746302, 11458190975,44395384830,167697083241,618401792448, 2228478398270,7854147511367] |