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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 19 |
| 3 | 103 |
| 4 | 634 |
| 5 | 4393 |
| 6 | 33893 |
| 7 | 288158 |
| 8 | 2674849 |
| 9 | 26888251 |
| 10 | 290614732 |
| 11 | 3356438587 |
| 12 | 41203019361 |
| 13 | 535141595208 |
| 14 | 7324289215167 |
| 15 | 105271669493307 |
| 16 | 1584113665608394 |
| 17 | 24890073684310405 |
| 18 | 407378999173905545 |
| 19 | 6930779764599424550 |
| 20 | 122334506551009552893 |
| 21 | 2236412875771806004767 |
[1,4,19,103,634,4393,33893,288158,2674849, 26888251,290614732,3356438587,41203019361, 535141595208,7324289215167,105271669493307, 1584113665608394,24890073684310405, 407378999173905545,6930779764599424550, 122334506551009552893,2236412875771806004767] |