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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 21 |
| 2 | 259 |
| 3 | 2570 |
| 4 | 18546 |
| 5 | 106067 |
| 6 | 508484 |
| 7 | 2117690 |
| 8 | 7852836 |
| 9 | 26400811 |
| 10 | 81594028 |
| 11 | 234380304 |
| 12 | 631352789 |
| 13 | 1606571023 |
| 14 | 3885713191 |
| 15 | 8979237218 |
| 16 | 19912769178 |
| 17 | 42540796862 |
| 18 | 87841523926 |
| 19 | 175820917355 |
| 20 | 341996038445 |
| 21 | 647926774508 |
| 22 | 1197980968295 |
| 23 | 2165529201795 |
| 24 | 3833173915877 |
[1,21,259,2570,18546,106067,508484,2117690, 7852836,26400811,81594028,234380304,631352789, 1606571023,3885713191,8979237218,19912769178, 42540796862,87841523926,175820917355,341996038445, 647926774508,1197980968295,2165529201795, 3833173915877] |