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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 22 |
| 3 | 133 |
| 4 | 813 |
| 5 | 4967 |
| 6 | 30349 |
| 7 | 185435 |
| 8 | 1133025 |
| 9 | 6922887 |
| 10 | 42299477 |
| 11 | 258453699 |
| 12 | 1579175897 |
| 13 | 9648910127 |
| 14 | 58955729261 |
| 15 | 360224933899 |
| 16 | 2201007512401 |
| 17 | 13448358549783 |
| 18 | 82170708943301 |
| 19 | 502070597184787 |
| 20 | 3067697574952457 |
[4,22,133,813,4967,30349,185435,1133025,6922887, 42299477,258453699,1579175897,9648910127, 58955729261,360224933899,2201007512401, 13448358549783,82170708943301,502070597184787, 3067697574952457] |