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 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 9 |
| 4 | 20 |
| 5 | 26 |
| 6 | 96 |
| 7 | -210 |
| 8 | 2472 |
| 9 | -20961 |
| 10 | 211612 |
| 11 | -2324729 |
| 12 | 27901116 |
| 13 | -362708320 |
| 14 | 5077925048 |
| 15 | -76168864092 |
| 16 | 1218701840976 |
| 17 | -20717931276243 |
| 18 | 372922762998708 |
| 19 | -7085532496941803 |
| 20 | 141710649938878564 |
| 21 | -2975923648716396714 |
| 22 | 65470320271760793488 |