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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 21 |
| 2 | 301 |
| 3 | 4088 |
| 4 | 55354 |
| 5 | 756059 |
| 6 | 10442117 |
| 7 | 145803900 |
| 8 | 2056351566 |
| 9 | 29262470042 |
| 10 | 419730456306 |
| 11 | 6062949606496 |
| 12 | 88127311401876 |
| 13 | 1288120149337735 |
| 14 | 18922077118169717 |
| 15 | 279209456350438708 |
| 16 | 4136682188907493702 |
| 17 | 61513664658938124486 |
| 18 | 917795824360157700870 |
[1,21,301,4088,55354,756059,10442117,145803900, 2056351566,29262470042,419730456306,6062949606496, 88127311401876,1288120149337735,18922077118169717, 279209456350438708,4136682188907493702, 61513664658938124486,917795824360157700870] |