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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 42 |
| 3 | 258 |
| 4 | 1590 |
| 5 | 9582 |
| 6 | 57786 |
| 7 | 347010 |
| 8 | 2083902 |
| 9 | 12505470 |
| 10 | 75044202 |
| 11 | 450278106 |
| 12 | 2701739022 |
| 13 | 16210513806 |
| 14 | 97263509010 |
| 15 | 583581545466 |
| 16 | 3501491846046 |
| 17 | 21008954050422 |
| 18 | 126053739826530 |
| 19 | 756322456907130 |
| 20 | 4537934834757702 |
| 21 | 27227609116759302 |
| 22 | 163365655261094322 |
[1,6,42,258,1590,9582,57786,347010,2083902, 12505470,75044202,450278106,2701739022, 16210513806,97263509010,583581545466, 3501491846046,21008954050422,126053739826530, 756322456907130,4537934834757702, 27227609116759302,163365655261094322] |