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 | 7 |
| 4 | -79 |
| 5 | 1201 |
| 6 | -22961 |
| 7 | 530167 |
| 8 | -14372191 |
| 9 | 447825889 |
| 10 | -15776617249 |
| 11 | 620209389031 |
| 12 | -26918670325295 |
| 13 | 1278598424153233 |
| 14 | -65973615445792081 |
| 15 | 3674793950748867031 |
| 16 | -219773335672937703871 |
| 17 | 14046128883828030510529 |
| 18 | -955409650156763223984449 |