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 | 2 |
| 2 | -3 |
| 3 | 22 |
| 4 | -138 |
| 5 | 1012 |
| 6 | -7839 |
| 7 | 63506 |
| 8 | -531024 |
| 9 | 4549276 |
| 10 | -39723484 |
| 11 | 352237844 |
| 12 | -3163252976 |
| 13 | 28711196184 |
| 14 | -262964888021 |
| 15 | 2427319896584 |
| 16 | -22557930343459 |
| 17 | 210889624536396 |
| 18 | -1981972609174109 |
| 19 | 18714482015314016 |
| 20 | -177453862702083994 |
| 21 | 1689045253793239952 |