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 | -1 |
| 4 | 11 |
| 5 | 19 |
| 6 | -311 |
| 7 | -1919 |
| 8 | 20201 |
| 9 | 154169 |
| 10 | -1363249 |
| 11 | -14236289 |
| 12 | 140759299 |
| 13 | 1213688059 |
| 14 | -33239720359 |
| 15 | -257577468511 |
| 16 | 11707385639249 |
| 17 | 119005356808561 |
| 18 | -3416942071608929 |
| 19 | -43117983466829441 |
| 20 | 893917358612502011 |
| 21 | 13133282766425234531 |
| 22 | -411010168576899605911 |
| 23 | -7970128344774479644991 |