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 | 3 |
| 2 | -3 |
| 3 | 9 |
| 4 | -33 |
| 5 | 126 |
| 6 | -513 |
| 7 | 2214 |
| 8 | -9876 |
| 9 | 45045 |
| 10 | -209493 |
| 11 | 990198 |
| 12 | -4741191 |
| 13 | 22946247 |
| 14 | -112079214 |
| 15 | 551793303 |
| 16 | -2735330190 |
| 17 | 13641353118 |
| 18 | -68394016548 |
| 19 | 344539469889 |
| 20 | -1743035351958 |
| 21 | 8851923849123 |
| 22 | -45110440515753 |
| 23 | 230615809867476 |
| 24 | -1182376529280117 |
| 25 | 6078184963674498 |
| 26 | -31322206517658453 |
| 27 | 161774639164275552 |
| 28 | -837290923919381322 |