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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 31 |
| 2 | 149 |
| 3 | 725 |
| 4 | 3543 |
| 5 | 17361 |
| 6 | 85223 |
| 7 | 418899 |
| 8 | 2061105 |
| 9 | 10149405 |
| 10 | 50011235 |
| 11 | 246566635 |
| 12 | 1216199805 |
| 13 | 6001382075 |
| 14 | 29624479933 |
| 15 | 146279954561 |
| 16 | 722500541847 |
| 17 | 3569422111283 |
| 18 | 17638150070523 |
| 19 | 87175432519409 |
| 20 | 430936179702041 |
[1,31,149,725,3543,17361,85223,418899,2061105, 10149405,50011235,246566635,1216199805,6001382075, 29624479933,146279954561,722500541847, 3569422111283,17638150070523,87175432519409, 430936179702041] |