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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 26 |
| 3 | 148 |
| 4 | 867 |
| 5 | 5048 |
| 6 | 29428 |
| 7 | 171512 |
| 8 | 999653 |
| 9 | 5826396 |
| 10 | 33958734 |
| 11 | 197925996 |
| 12 | 1153597255 |
| 13 | 6723657520 |
| 14 | 39188347880 |
| 15 | 228406429744 |
| 16 | 1331250230601 |
| 17 | 7759094953844 |
| 18 | 45223319492482 |
| 19 | 263580822001028 |
| 20 | 1536261612513707 |
| 21 | 8953988853081192 |
| 22 | 52187671505973468 |
[1,4,26,148,867,5048,29428,171512,999653,5826396, 33958734,197925996,1153597255,6723657520, 39188347880,228406429744,1331250230601, 7759094953844,45223319492482,263580822001028, 1536261612513707,8953988853081192, 52187671505973468] |