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 | -7 |
| 3 | 56 |
| 4 | -532 |
| 5 | 5600 |
| 6 | -62860 |
| 7 | 737324 |
| 8 | -8929726 |
| 9 | 110811344 |
| 10 | -1401640814 |
| 11 | 18004922936 |
| 12 | -234243536436 |
| 13 | 3080152906096 |
| 14 | -40870739065996 |
| 15 | 546563064528906 |
| 16 | -7358930622768977 |
| 17 | 99672580921800656 |
| 18 | -1357142384455626909 |
| 19 | 18565841939010374736 |
| 20 | -255054402946387767408 |