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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 28 |
| 3 | 89 |
| 4 | 361 |
| 5 | 1620 |
| 6 | 6392 |
| 7 | 26243 |
| 8 | 109483 |
| 9 | 447624 |
| 10 | 1841540 |
| 11 | 7595029 |
| 12 | 31226203 |
| 13 | 128506736 |
| 14 | 529054684 |
| 15 | 2177033731 |
| 16 | 8959709123 |
| 17 | 36876424418 |
| 18 | 151764857870 |
| 19 | 624602187635 |
| 20 | 2570631663169 |
| 21 | 10579647127402 |
| 22 | 43541564503936 |
[4,28,89,361,1620,6392,26243,109483,447624, 1841540,7595029,31226203,128506736,529054684, 2177033731,8959709123,36876424418,151764857870, 624602187635,2570631663169,10579647127402, 43541564503936] |