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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 5 |
| 3 | 26 |
| 4 | 208 |
| 5 | 1644 |
| 6 | 18728 |
| 7 | 201466 |
| 8 | 2809672 |
| 9 | 39505800 |
| 10 | 647509992 |
| 11 | 10851033984 |
| 12 | 210456343392 |
| 13 | 4090234000800 |
| 14 | 89123794754304 |
| 15 | 2000019423403824 |
| 16 | 48674645933985408 |
| 17 | 1217362548455301504 |
| 18 | 32913123947574009984 |
| 19 | 910006995701419453440 |
| 20 | 26898048642355515339264 |
[1,1,5,26,208,1644,18728,201466,2809672,39505800, 647509992,10851033984,210456343392,4090234000800, 89123794754304,2000019423403824,48674645933985408, 1217362548455301504,32913123947574009984, 910006995701419453440,26898048642355515339264] |