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 | 0 |
| 2 | -2 |
| 3 | -6 |
| 4 | -12 |
| 5 | -10 |
| 6 | 60 |
| 7 | 406 |
| 8 | 672 |
| 9 | -18666 |
| 10 | -400740 |
| 11 | -6617842 |
| 12 | -108686952 |
| 13 | -1883464466 |
| 14 | -34930602252 |
| 15 | -693981413610 |
| 16 | -14732243810016 |
| 17 | -333084114060442 |
| 18 | -7994768036250132 |
| 19 | -203102355108133154 |
| 20 | -5445884954606704920 |
| 21 | -153726156157794541986 |