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| n | a(n) |
|---|---|
| 1 | 50 |
| 2 | 170 |
| 3 | 558 |
| 4 | 1906 |
| 5 | 6386 |
| 6 | 21940 |
| 7 | 74714 |
| 8 | 258496 |
| 9 | 891586 |
| 10 | 3106540 |
| 11 | 10821426 |
| 12 | 37946232 |
| 13 | 133190826 |
| 14 | 469570860 |
| 15 | 1657721338 |
| 16 | 5869905680 |
| 17 | 20812541098 |
| 18 | 73947974244 |
| 19 | 263041695362 |
| 20 | 937043382992 |
| 21 | 3341162160402 |
| 22 | 11925776401308 |
[50,170,558,1906,6386,21940,74714,258496,891586, 3106540,10821426,37946232,133190826,469570860, 1657721338,5869905680,20812541098,73947974244, 263041695362,937043382992,3341162160402, 11925776401308] |