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 | 5 |
| 4 | 7 |
| 5 | -71 |
| 6 | -139 |
| 7 | 2071 |
| 8 | 5335 |
| 9 | -103207 |
| 10 | -331511 |
| 11 | 7853251 |
| 12 | 30256381 |
| 13 | -847377805 |
| 14 | -3808492297 |
| 15 | 123081031165 |
| 16 | 632196102455 |
| 17 | -23155450005175 |
| 18 | -133802756269735 |
| 19 | 5477371955388355 |
| 20 | 35167483918412257 |
| 21 | -1591161899246627297 |
| 22 | -11237664710770159597 |
| 23 | 556875003328690925825 |
| 24 | 4290500676272573740429 |