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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 19 |
| 4 | 128 |
| 5 | 929 |
| 6 | 9008 |
| 7 | 88677 |
| 8 | 1068496 |
| 9 | 13585713 |
| 10 | 195465552 |
| 11 | 2962147101 |
| 12 | 50411419368 |
| 13 | 887757722409 |
| 14 | 17125724016984 |
| 15 | 346462040798229 |
| 16 | 7503508038803616 |
| 17 | 169554609033560673 |
| 18 | 4085808543521351136 |
| 19 | 102156453049201047981 |
[1,1,4,19,128,929,9008,88677,1068496,13585713, 195465552,2962147101,50411419368,887757722409, 17125724016984,346462040798229,7503508038803616, 169554609033560673,4085808543521351136, 102156453049201047981] |