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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 28 |
| 3 | 268 |
| 4 | 3148 |
| 5 | 43564 |
| 6 | 692428 |
| 7 | 12390508 |
| 8 | 245896588 |
| 9 | 5351817004 |
| 10 | 126614238028 |
| 11 | 3232332423148 |
| 12 | 88500275727628 |
| 13 | 2585371577628844 |
| 14 | 80227707005300428 |
| 15 | 2634361286274638188 |
| 16 | 91223969834203056268 |
| 17 | 3321457538305952791084 |
| 18 | 126817592900018186967628 |
[1,4,28,268,3148,43564,692428,12390508,245896588, 5351817004,126614238028,3232332423148, 88500275727628,2585371577628844,80227707005300428, 2634361286274638188,91223969834203056268, 3321457538305952791084,126817592900018186967628] |