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 | -21 |
| 2 | 189 |
| 3 | -952 |
| 4 | 3087 |
| 5 | -8400 |
| 6 | 27503 |
| 7 | -92907 |
| 8 | 246981 |
| 9 | -588490 |
| 10 | 1649823 |
| 11 | -4645179 |
| 12 | 10989769 |
| 13 | -25476717 |
| 14 | 65615424 |
| 15 | -161705810 |
| 16 | 363998754 |
| 17 | -834169539 |
| 18 | 1973130271 |
| 19 | -4510112565 |
| 20 | 9969930495 |
| 21 | -22054706773 |