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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 23 |
| 4 | 199 |
| 5 | 2313 |
| 6 | 34015 |
| 7 | 606407 |
| 8 | 12712643 |
| 9 | 306407645 |
| 10 | 8346154699 |
| 11 | 253476928293 |
| 12 | 8490863621050 |
| 13 | 310937199521774 |
| 14 | 12356288017546937 |
| 15 | 529516578044589407 |
| 16 | 24339848939829286381 |
| 17 | 1194495870124420574751 |
| 18 | 62332449791125883072149 |
| 19 | 3446265450868329833016605 |
[1,1,4,23,199,2313,34015,606407,12712643, 306407645,8346154699,253476928293,8490863621050, 310937199521774,12356288017546937, 529516578044589407,24339848939829286381, 1194495870124420574751,62332449791125883072149, 3446265450868329833016605] |