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 | 1 |
| 2 | 1 |
| 3 | 0 |
| 4 | -3 |
| 5 | -4 |
| 6 | 21 |
| 7 | 80 |
| 8 | -263 |
| 9 | -2224 |
| 10 | 4841 |
| 11 | 88960 |
| 12 | -99723 |
| 13 | -4942144 |
| 14 | -199939 |
| 15 | 366928640 |
| 16 | 501445617 |
| 17 | -35219691264 |
| 18 | -101818966319 |
| 19 | 4251941253120 |
| 20 | 19731909099757 |
| 21 | -631113275843584 |
| 22 | -4192563651606299 |
| 23 | 113005305852006400 |
| 24 | 1009030667701246697 |