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 | 4 |
| 3 | 1 |
| 4 | -152 |
| 5 | -3515 |
| 6 | -54080 |
| 7 | -671363 |
| 8 | -2823296 |
| 9 | 199955305 |
| 10 | 10101514240 |
| 11 | 323321153881 |
| 12 | 7583054076928 |
| 13 | 80180394219757 |
| 14 | -4570380001660928 |
| 15 | -409907196093564395 |
| 16 | -20705306119297925120 |
| 17 | -748794938843475359663 |
| 18 | -14289862480447260852224 |
| 19 | 610587389113316064978481 |