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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 25 |
| 3 | 199 |
| 4 | 1795 |
| 5 | 17422 |
| 6 | 177463 |
| 7 | 1870960 |
| 8 | 20241403 |
| 9 | 223438852 |
| 10 | 2506596547 |
| 11 | 28494103183 |
| 12 | 327507800725 |
| 13 | 3799735202218 |
| 14 | 44440058006593 |
| 15 | 523388751658831 |
| 16 | 6201937444137619 |
| 17 | 73888034816382820 |
| 18 | 884517283667145259 |
| 19 | 10634234680321209373 |
| 20 | 128347834921058404249 |
[1,4,25,199,1795,17422,177463,1870960,20241403, 223438852,2506596547,28494103183,327507800725, 3799735202218,44440058006593,523388751658831, 6201937444137619,73888034816382820, 884517283667145259,10634234680321209373, 128347834921058404249] |