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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 23 |
| 3 | 141 |
| 4 | 888 |
| 5 | 5676 |
| 6 | 36622 |
| 7 | 237821 |
| 8 | 1551727 |
| 9 | 10161409 |
| 10 | 66732392 |
| 11 | 439267525 |
| 12 | 2897064773 |
| 13 | 19137833146 |
| 14 | 126599140313 |
| 15 | 838477244705 |
| 16 | 5559158604616 |
| 17 | 36891869005316 |
| 18 | 245025744759152 |
| 19 | 1628602268643928 |
| 20 | 10832010390274304 |
| 21 | 72088640151558145 |
| 22 | 480026332241373281 |
| 23 | 3198037386794785777 |
| 24 | 21315944308822771118 |
[1,4,23,141,888,5676,36622,237821,1551727, 10161409,66732392,439267525,2897064773, 19137833146,126599140313,838477244705, 5559158604616,36891869005316,245025744759152, 1628602268643928,10832010390274304, 72088640151558145,480026332241373281, 3198037386794785777,21315944308822771118] |