This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | -1 |
| 1 | -1 |
| 2 | -1 |
| 3 | 7 |
| 4 | 127 |
| 5 | 1711 |
| 6 | 23231 |
| 7 | 334391 |
| 8 | 5144063 |
| 9 | 84149983 |
| 10 | 1446872959 |
| 11 | 25661798119 |
| 12 | 454494403199 |
| 13 | 7489030040207 |
| 14 | 89680375568447 |
| 15 | -759618144120809 |
| 16 | -127049044802971649 |
| 17 | -7480338932613448769 |
| 18 | -369274690558092738817 |
| 19 | -17262533154073740329017 |